Version 6.0.12 brings several changes:

* re-enabled import of downloaded media files, which can be used to migrate from 5.5.4. Media files imported are restricted to existing feeds and episodes.
* importing media files is only allowed from a directory with name containing "Podcini-MediaFiles"
* if you have imported some media files exported from 5.5.4 using version 6.0.10, these files are junk. You can opt for clearing storage or re-installing version 6, or you can ignore them for now as I plan to provide media file management functionality in the near future.