Most of the TV shows in my library have incorrect video preview thumbnails. I don;t know why, but they nearly all show scenes from one particular Futurama episode, no matter what the show. Some of the first shows I added to the library are ok (i.e. show thumbnails rendered from the actual show), but none of the later ones.
I have experimented with rebuilding the media index files using the command line Plex Media Scanner: $ ./Plex\ Media\ Scanner -l 7: Audiobooks 1: Movies 4: Music 3: Photos 2: TV Shows $ ./Plex\ Media\ Scanner -b -c 2
but to no avail. Curiously if I play “optimised versions” of the same files that Plex generates for iOS devices, the video preview thumbnails are fine.
I had this problem a year and a half ago (https://forums.plex.tv/discussion/177699/wrong-generated-preview-thumbnails#latest). I never got a clear answer. The only suggestion was to mess around with command line and I didn’t quite have the time to do that. The problem was only remedied because I moved to another server and the thumbnails were rebuilt.
You could delete the thumbnails for the whole library, depending on the size, and remake them. I have no idea if this would actually work, not to mention it would be a lot of wasted CPU cycles.
It seems as though “Plex Dancing” affected shows is enough. I suspect the issue may result from using Handbrake to transcode direct into the share that Plex is watching, with the result that it detects changes & starts to scan the library before the transcode is complete.
