Gotcha. I do not run PMS on Linux, but other than the Synology specific info that shouldn’t matter (I run PMS on a DS918+).
I’ve never seen that happen.
A couple of thoughts if the Plex Dance doesn’t clear things up.
First, check the metadata in the file. Make sure there is not conflicting / duplicate info in the Title field. The Title field does not need to be populated. Plex should match things with TheTVDB based on the file name.
You can click on View XML or use MediaInfo to view the info. You can use the Header Editor in MKVToolNix to modify things if needed.
Second, if all else fails, you should be able to split the files.
