diff --git a/modules/interventi/ajax_tecnici.php b/modules/interventi/ajax_tecnici.php
index 47c642152..f2d6a6e10 100755
--- a/modules/interventi/ajax_tecnici.php
+++ b/modules/interventi/ajax_tecnici.php
@@ -143,7 +143,7 @@ if (!empty($sessioni)) {
 
         // ORE
         echo '
-        <td style="border-right:1px solid #aaa;">'.($ore <= 0 ? '<i  title="'.tr('Questa sessione non ha una durata valida.').'" class="fa fa-warning tip text-warning"></i>' : '').' 
+        <td style="border-right:1px solid #aaa;">'.(((\Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $sessione['orario_inizio'])->eq(\Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $sessione['orario_fine']))) || (\Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $sessione['orario_inizio'])->gt(\Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $sessione['orario_fine']))))  ? '<i  title="'.tr('Questa sessione non ha una durata valida.').'" class="fa fa-warning tip text-warning"></i>' : '').' 
         </td>
         <td style="border-right:1px solid #aaa;"> 
             {[ "type": "number", "name": "ore_'.$sessione['id'].'", "required": 1, "value": "'.numberFormat($ore, 'qta').'", "disabled": "1" ]}
diff --git a/src/Prints.php b/src/Prints.php
index 5b954649d..694680fe5 100755
--- a/src/Prints.php
+++ b/src/Prints.php
@@ -260,7 +260,7 @@ class Prints
     {
         $info = self::render($print, $id_record, $directory);
 
-        return self::getPDFLink($info['path']);
+        return self::getPDFLink($info['path'].'?'.rand());
     }
 
     /**
@@ -272,7 +272,7 @@ class Prints
      */
     public static function getPDFLink($path)
     {
-        return base_path().'/assets/dist/pdfjs/web/viewer.html?file='.base_url().'/'.ltrim(str_replace(base_dir(), '', $path), '/');
+        return base_path().'/assets/dist/pdfjs/web/viewer.html?file='.base_url().'/'.ltrim(str_replace(base_dir(), '', $path.'?'.rand()), '/');
     }
 
     /**