Using the following GPodder options, MKV files that are downloaded are not renamed properly.

1. Youtube-dl extension is in use with the "bestvideo+bestaudio" option.
2. Rename Episodes extension is in use.

If an MP4 or WEBM file is downloaded, the renaming works properly. If an MKV file is downloaded it is not renamed and a zero-byte MP4 file is created that is properly named.

I don't have example video links available right now but will have them in a day or two.