diff --git a/.circleci/config.yml b/.circleci/config.yml
index 80dbab808..c2eea438d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -94,8 +94,5 @@ workflows:
           name: SpotBugs
           build-steps:
             - run:
-                name: SpotBugs (Modules with Play flavour)
-                command: ./gradlew spotbugsPlayDebug | grep "\[SpotBugs\]"
-            - run:
-                name: SpotBugs (Modules without Play flavour)
-                command: ./gradlew spotbugsDebug | grep "\[SpotBugs\]"
+                name: SpotBugs
+                command: ./gradlew spotbugsPlayDebug spotbugsDebug 2>&1 | grep -i "spotbugs"
diff --git a/app/src/main/java/de/danoeh/antennapod/activity/MainActivity.java b/app/src/main/java/de/danoeh/antennapod/activity/MainActivity.java
index b5edcc878..aa1d746a5 100644
--- a/app/src/main/java/de/danoeh/antennapod/activity/MainActivity.java
+++ b/app/src/main/java/de/danoeh/antennapod/activity/MainActivity.java
@@ -188,7 +188,9 @@ public class MainActivity extends CastEnabledActivity {
 
     public void setupToolbarToggle(@NonNull Toolbar toolbar, boolean displayUpArrow) {
         if (drawerLayout != null) { // Tablet layout does not have a drawer
-            drawerLayout.removeDrawerListener(drawerToggle);
+            if (drawerToggle != null) {
+                drawerLayout.removeDrawerListener(drawerToggle);
+            }
             drawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar,
                     R.string.drawer_open, R.string.drawer_close);
             drawerLayout.addDrawerListener(drawerToggle);
diff --git a/app/src/main/java/de/danoeh/antennapod/adapter/NavListAdapter.java b/app/src/main/java/de/danoeh/antennapod/adapter/NavListAdapter.java
index de3242b1a..05099777c 100644
--- a/app/src/main/java/de/danoeh/antennapod/adapter/NavListAdapter.java
+++ b/app/src/main/java/de/danoeh/antennapod/adapter/NavListAdapter.java
@@ -58,9 +58,8 @@ public class NavListAdapter extends RecyclerView.Adapter<NavListAdapter.Holder>
      */
     public static final String SUBSCRIPTION_LIST_TAG = "SubscriptionList";
 
-    private static List<String> fragmentTags;
-    private static String[] titles;
-
+    private final List<String> fragmentTags = new ArrayList<>();
+    private final String[] titles;
     private final ItemAccess itemAccess;
     private final WeakReference<Activity> activity;
     public boolean showSubscriptionList = true;
@@ -98,7 +97,8 @@ public class NavListAdapter extends RecyclerView.Adapter<NavListAdapter.Holder>
             showSubscriptionList = false;
         }
 
-        fragmentTags = newTags;
+        fragmentTags.clear();
+        fragmentTags.addAll(newTags);
         notifyDataSetChanged();
     }
 
diff --git a/app/src/main/java/de/danoeh/antennapod/dialog/ProxyDialog.java b/app/src/main/java/de/danoeh/antennapod/dialog/ProxyDialog.java
index d0fb91692..375f676c8 100644
--- a/app/src/main/java/de/danoeh/antennapod/dialog/ProxyDialog.java
+++ b/app/src/main/java/de/danoeh/antennapod/dialog/ProxyDialog.java
@@ -206,7 +206,7 @@ public class ProxyDialog {
 
     private boolean checkPort() {
         int port = getPort();
-        if(port < 0 && port > 65535) {
+        if (port < 0 || port > 65535) {
             etPort.setError(context.getString(R.string.proxy_port_invalid_error));
             return false;
         }
diff --git a/app/src/main/java/de/danoeh/antennapod/discovery/PodcastSearcherRegistry.java b/app/src/main/java/de/danoeh/antennapod/discovery/PodcastSearcherRegistry.java
index 16c5548be..dfea627df 100644
--- a/app/src/main/java/de/danoeh/antennapod/discovery/PodcastSearcherRegistry.java
+++ b/app/src/main/java/de/danoeh/antennapod/discovery/PodcastSearcherRegistry.java
@@ -12,7 +12,7 @@ public class PodcastSearcherRegistry {
     private PodcastSearcherRegistry() {
     }
 
-    public static List<SearcherInfo> getSearchProviders() {
+    public static synchronized List<SearcherInfo> getSearchProviders() {
         if (searchProviders == null) {
             searchProviders = new ArrayList<>();
             searchProviders.add(new SearcherInfo(new CombinedSearcher(), 1.0f));
diff --git a/app/src/main/java/de/danoeh/antennapod/error/CrashReportWriter.java b/app/src/main/java/de/danoeh/antennapod/error/CrashReportWriter.java
index dc62863f9..23c8ffdd5 100644
--- a/app/src/main/java/de/danoeh/antennapod/error/CrashReportWriter.java
+++ b/app/src/main/java/de/danoeh/antennapod/error/CrashReportWriter.java
@@ -7,7 +7,6 @@ import de.danoeh.antennapod.BuildConfig;
 import org.apache.commons.io.IOUtils;
 
 import java.io.File;
-import java.io.FileWriter;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.text.SimpleDateFormat;
@@ -40,7 +39,7 @@ public class CrashReportWriter implements Thread.UncaughtExceptionHandler {
         File path = getFile();
         PrintWriter out = null;
         try {
-            out = new PrintWriter(new FileWriter(path));
+            out = new PrintWriter(path, "UTF-8");
             out.println("## Crash info");
             out.println("Time: " + new SimpleDateFormat("dd-MM-yyyy HH:mm:ss", Locale.getDefault()).format(new Date()));
             out.println("AntennaPod version: " + BuildConfig.VERSION_NAME);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
index 612959c04..18b011a08 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
@@ -27,7 +27,7 @@ public class AllEpisodesFragment extends EpisodesListFragment {
     private static final String PREF_NAME = "PrefAllEpisodesFragment";
     private static final String PREF_FILTER = "filter";
 
-    private static FeedItemFilter feedItemFilter = new FeedItemFilter("");
+    private FeedItemFilter feedItemFilter = new FeedItemFilter("");
 
     @Override
     public void onCreate(@Nullable Bundle savedInstanceState) {
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/gpodnet/TagFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/gpodnet/TagFragment.java
index 0ce38656a..0d9181d84 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/gpodnet/TagFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/gpodnet/TagFragment.java
@@ -1,13 +1,13 @@
 package de.danoeh.antennapod.fragment.gpodnet;
 
 import android.os.Bundle;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import de.danoeh.antennapod.core.sync.gpoddernet.GpodnetService;
 import de.danoeh.antennapod.core.sync.gpoddernet.GpodnetServiceException;
 import de.danoeh.antennapod.core.sync.gpoddernet.model.GpodnetPodcast;
 import de.danoeh.antennapod.core.sync.gpoddernet.model.GpodnetTag;
-import org.apache.commons.lang3.Validate;
 
 import de.danoeh.antennapod.activity.MainActivity;
 
@@ -24,8 +24,7 @@ public class TagFragment extends PodcastListFragment {
 
     private GpodnetTag tag;
 
-    public static TagFragment newInstance(GpodnetTag tag) {
-        Validate.notNull(tag);
+    public static TagFragment newInstance(@NonNull GpodnetTag tag) {
         TagFragment fragment = new TagFragment();
         Bundle args = new Bundle();
         args.putParcelable("tag", tag);
@@ -38,7 +37,9 @@ public class TagFragment extends PodcastListFragment {
         super.onCreate(savedInstanceState);
 
         Bundle args = getArguments();
-        Validate.isTrue(args != null && args.getParcelable("tag") != null, "args invalid");
+        if (args == null || args.getParcelable("tag") == null) {
+            throw new IllegalArgumentException("Arguments not given");
+        }
         tag = args.getParcelable("tag");
     }
 
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/DevelopersFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/DevelopersFragment.java
index b844234b7..dcd720dc2 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/DevelopersFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/DevelopersFragment.java
@@ -29,7 +29,7 @@ public class DevelopersFragment extends ListFragment {
         developersLoader = Single.create((SingleOnSubscribe<ArrayList<SimpleIconListAdapter.ListItem>>) emitter -> {
             ArrayList<SimpleIconListAdapter.ListItem> developers = new ArrayList<>();
             BufferedReader reader = new BufferedReader(new InputStreamReader(
-                    getContext().getAssets().open("developers.csv")));
+                    getContext().getAssets().open("developers.csv"), "UTF-8"));
             String line;
             while ((line = reader.readLine()) != null) {
                 String[] info = line.split(";");
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/LicensesFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/LicensesFragment.java
index 97565a613..38e532aed 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/LicensesFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/LicensesFragment.java
@@ -95,7 +95,7 @@ public class LicensesFragment extends ListFragment {
     private void showLicenseText(String licenseTextFile) {
         try {
             BufferedReader reader = new BufferedReader(new InputStreamReader(
-                    getContext().getAssets().open(licenseTextFile)));
+                    getContext().getAssets().open(licenseTextFile), "UTF-8"));
             StringBuilder licenseText = new StringBuilder();
             String line;
             while ((line = reader.readLine()) != null) {
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/SpecialThanksFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/SpecialThanksFragment.java
index d759a5ff2..1b4beeea0 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/SpecialThanksFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/SpecialThanksFragment.java
@@ -29,7 +29,7 @@ public class SpecialThanksFragment extends ListFragment {
         translatorsLoader = Single.create((SingleOnSubscribe<ArrayList<SimpleIconListAdapter.ListItem>>) emitter -> {
             ArrayList<SimpleIconListAdapter.ListItem> translators = new ArrayList<>();
             BufferedReader reader = new BufferedReader(new InputStreamReader(
-                    getContext().getAssets().open("special_thanks.csv")));
+                    getContext().getAssets().open("special_thanks.csv"), "UTF-8"));
             String line;
             while ((line = reader.readLine()) != null) {
                 String[] info = line.split(";");
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/TranslatorsFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/TranslatorsFragment.java
index b77c74de6..ed0d53145 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/TranslatorsFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/preferences/about/TranslatorsFragment.java
@@ -29,7 +29,7 @@ public class TranslatorsFragment extends ListFragment {
         translatorsLoader = Single.create((SingleOnSubscribe<ArrayList<SimpleIconListAdapter.ListItem>>) emitter -> {
             ArrayList<SimpleIconListAdapter.ListItem> translators = new ArrayList<>();
             BufferedReader reader = new BufferedReader(new InputStreamReader(
-                    getContext().getAssets().open("translators.csv")));
+                    getContext().getAssets().open("translators.csv"), "UTF-8"));
             String line;
             while ((line = reader.readLine()) != null) {
                 String[] info = line.split(";");
diff --git a/config/spotbugs/exclude.xml b/config/spotbugs/exclude.xml
index 4c1e23ece..c2e97c780 100644
--- a/config/spotbugs/exclude.xml
+++ b/config/spotbugs/exclude.xml
@@ -1,13 +1,39 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <FindBugsFilter>
     <Match>
-        <Bug pattern="v   WEAK_MESSAGE_DIGEST_MD5"/>
+        <Bug pattern="DM_DEFAULT_ENCODING"/>
+        <Class name="de.danoeh.antennapod.core.util.vorbiscommentreader.VorbisCommentReader"/>
     </Match>
     <Match>
-        <Bug pattern="v  LI_LAZY_INIT_UPDATE_STATIC"/>
+        <Bug pattern="MS_MUTABLE_ARRAY"/>
+        <Class name="de.danoeh.antennapod.fragment.NavDrawerFragment"/>
+    </Match>
+    <Match>
+        <Bug pattern="MS_SHOULD_BE_FINAL"/>
+        <Class name="de.danoeh.antennapod.core.ClientConfig"/>
     </Match>
     <Match>
         <Bug pattern="NM_SAME_SIMPLE_NAME_AS_SUPERCLASS"/>
         <Class name="de.danoeh.antennapod.menuhandler.MenuItemUtils"/>
     </Match>
+    <Match>
+        <Bug pattern="NP_NONNULL_PARAM_VIOLATION"/>
+        <Class name="de.danoeh.antennapod.activity.MainActivity"/>
+    </Match>
+    <Match>
+        <Bug pattern="NP_NULL_ON_SOME_PATH"/>
+        <Class name="de.danoeh.antennapod.activity.MainActivity"/>
+    </Match>
+    <Match>
+        <Bug pattern="NP_NULL_ON_SOME_PATH"/>
+        <Class name="de.danoeh.antennapod.core.feed.FeedMedia"/>
+    </Match>
+    <Match>
+        <Bug pattern="NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE"/>
+        <Class name="de.danoeh.antennapod.dialog.PlaybackControlsDialog"/>
+    </Match>
+    <Match>
+        <Bug pattern="NP_NULL_PARAM_DEREF"/>
+        <Class name="de.danoeh.antennapod.core.feed.FeedMedia"/>
+    </Match>
 </FindBugsFilter>
diff --git a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
index d6926385e..47df099b5 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
@@ -43,7 +43,7 @@ public class FeedItem extends FeedComponent implements Serializable {
     private Date pubDate;
     private FeedMedia media;
 
-    private Feed feed;
+    private transient Feed feed;
     private long feedId;
 
     private int state;
diff --git a/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java b/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
index 519d625e2..d6d63fed0 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
@@ -1,7 +1,6 @@
 package de.danoeh.antennapod.core.glide;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import com.bumptech.glide.Priority;
 import com.bumptech.glide.load.DataSource;
 import com.bumptech.glide.load.Options;
@@ -36,7 +35,6 @@ public final class ChapterImageModelLoader implements ModelLoader<EmbeddedChapte
         }
     }
 
-    @Nullable
     @Override
     public LoadData<ByteBuffer> buildLoadData(@NonNull EmbeddedChapterImage model,
                                               int width,
@@ -65,9 +63,9 @@ public final class ChapterImageModelLoader implements ModelLoader<EmbeddedChapte
                 if (image.getMedia().localFileAvailable()) {
                     File localFile = new File(image.getMedia().getLocalMediaUrl());
                     stream = new BufferedInputStream(new FileInputStream(localFile));
-                    stream.skip(image.getPosition());
+                    IOUtils.skip(stream, image.getPosition());
                     byte[] imageContent = new byte[image.getLength()];
-                    stream.read(imageContent, 0, image.getLength());
+                    IOUtils.read(stream, imageContent, 0, image.getLength());
                     callback.onDataReady(ByteBuffer.wrap(imageContent));
                 } else {
                     Request.Builder httpReq = new Request.Builder();
@@ -88,10 +86,13 @@ public final class ChapterImageModelLoader implements ModelLoader<EmbeddedChapte
             }
         }
 
-        @Override public void cleanup() {
+        @Override
+        public void cleanup() {
             // nothing to clean up
         }
-        @Override public void cancel() {
+
+        @Override
+        public void cancel() {
             // cannot cancel
         }
 
diff --git a/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java b/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
index 1f8ae5ad9..4de6a7315 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
@@ -8,6 +8,7 @@ import android.util.Log;
 import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
 import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;
 
+import java.nio.charset.Charset;
 import java.security.MessageDigest;
 
 public class FastBlurTransformation extends BitmapTransformation {
@@ -43,7 +44,7 @@ public class FastBlurTransformation extends BitmapTransformation {
 
     @Override
     public void updateDiskCacheKey(@NonNull MessageDigest messageDigest) {
-        messageDigest.update(TAG.getBytes());
+        messageDigest.update(TAG.getBytes(Charset.defaultCharset()));
     }
 
     private static Bitmap fastBlur(Bitmap bitmap, int radius) {
diff --git a/core/src/main/java/de/danoeh/antennapod/core/service/download/AntennapodHttpClient.java b/core/src/main/java/de/danoeh/antennapod/core/service/download/AntennapodHttpClient.java
index c4029d57f..4d1d44908 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/service/download/AntennapodHttpClient.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/service/download/AntennapodHttpClient.java
@@ -120,7 +120,7 @@ public class AntennapodHttpClient {
             SocketAddress address = InetSocketAddress.createUnresolved(config.host, port);
             Proxy proxy = new Proxy(config.type, address);
             builder.proxy(proxy);
-            if (!TextUtils.isEmpty(config.username)) {
+            if (!TextUtils.isEmpty(config.username) && config.password != null) {
                 String credentials = Credentials.basic(config.username, config.password);
                 builder.interceptors().add(chain -> {
                     Request request = chain.request().newBuilder()
diff --git a/core/src/main/java/de/danoeh/antennapod/core/sync/gpoddernet/GpodnetService.java b/core/src/main/java/de/danoeh/antennapod/core/sync/gpoddernet/GpodnetService.java
index cecfc0d2c..cd0fc93ea 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/sync/gpoddernet/GpodnetService.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/sync/gpoddernet/GpodnetService.java
@@ -667,11 +667,11 @@ public class GpodnetService implements ISyncService {
             while ((count = in.read(buffer)) > 0) {
                 outputStream.write(buffer, 0, count);
             }
+            return outputStream.toString("UTF-8");
         } catch (IOException e) {
             e.printStackTrace();
             throw new GpodnetServiceException(e);
         }
-        return outputStream.toString();
     }
 
     private void checkStatusCode(@NonNull Response response) throws GpodnetServiceException {
diff --git a/core/src/main/java/de/danoeh/antennapod/core/util/syndication/HtmlToPlainText.java b/core/src/main/java/de/danoeh/antennapod/core/util/syndication/HtmlToPlainText.java
index baa467acf..37dee0486 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/util/syndication/HtmlToPlainText.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/util/syndication/HtmlToPlainText.java
@@ -34,8 +34,7 @@ import java.util.regex.Pattern;
 public class HtmlToPlainText {
 
     /**
-     * Use this method to strip off HTML encoding from given text
-     * <p>
+     * Use this method to strip off HTML encoding from given text.
      * Replaces bullet points with *, ignores colors/bold/...
      *
      * @param str String with any encoding
@@ -60,10 +59,8 @@ public class HtmlToPlainText {
      * @return <b>True</b> if text contains any HTML tags<br /><b>False</b> is no HTML tag is found
      */
     private static boolean isHtml(String str) {
-        final String HTML_TAG_PATTERN = "<(\"[^\"]*\"|'[^']*'|[^'\">])*>";
-        Pattern htmlValidator = TextUtils.isEmpty(HTML_TAG_PATTERN) ? null : Pattern.compile(HTML_TAG_PATTERN);
-
-        return htmlValidator.matcher(str).find();
+        final String htmlTagPattern = "<(\"[^\"]*\"|'[^']*'|[^'\">])*>";
+        return Pattern.compile(htmlTagPattern).matcher(str).find();
     }
 
     /**