Every few months, the thumbnails go blank. Not sure if it’s the same shows but it happens to around 20-50% of shows. The only way to fix it is to rematch the show. I’m on Debian PMS. It happens on the web and Android, and I assume for every client. I’ve been doing the plex dance before I found the “rematch” fix. So removing/purging/re-adding the files and letting the folders regenerate metadata from scratch doesn’t fix this issue, it just keeps coming back.
This happens for Korean and Chinese Shows but happens rarely for English shows. Is that a clue? I use PMM, but it doesn’t touch season or episode thumbnails.
Please, Plex gods, help me! lol, I’ve been dealing with this for maybe years now.
What types of files are they. what codecs do they use? Do they play fine and if you force a transcode by lowering quality do they transcode fine?
Neither of those shows seem to have any metadata images at TVDB or TMDB so wondering if some issue with the thumbs the the server creates via screen grabs which the transcoder makes.
Since you’re using Debian I am assuming you have some familiarity with using command line. I’m not sure why it is happening but you could use the --generate option to create them. ( afaik that command is not deprecated)
Yup they’re perfectly fine, and they’re HEVC encoded just like everything else that works fine. There’s nothing wrong with them playing at all.
I will check the --generate option. But just to mention, I can fix the problem and regenerate the thumbnails by doing a “fix match” and re-matching the show. It fixes the problem right away. So my suspicion is that something changes where it can’t find the generated thumbnails. The generated thumbnails are probably still inside the bundles, but I haven’t checked. I think I’ll check it now.
After “re-matching” the show. The user_thumb_url entry is updated/changed (on live db) and I can see the thumbnail file in my system and I confirmed it is the same thumbnail that is now showing for the epsiode. The file was created 2024-04-04 so it wasn’t created when I “re-matched” the show just now. It also now has a different hash bundle directory.
The media file (MKV) itself has a modification time of 2024-04-03, so a day before the thumbnail was created. I’ve had this file/show since 2022. Now I remember modifying the tracks of some of these MKV files, like setting audio language, or embedding subtitles, maybe remove some non-english subtitle tracks.
So now I wonder if this is because the file hash changes while the filesize remains exactly the same. It’s probably my edits that is confusing Plex. I use MKVToolNix/mkvmerge CLI to straighten files. But this happens randomly. Some shows are fine even after I make some edits.
If you don’t mind sharing your server logs after refreshing metadata for some show that is still not showing images I can give them to devs to have a look
So you’d like me to trigger a refresh metadata just on the show that’s missing, then save logs? I’ve been rematching them for a few hours now, but I still have more to go, so I’ll try and line up a few titles that have blank thumbnails, and I’ll refresh them all one by one.
I checked the same file that was generated earlier after I did the “rematch” trick (the same file I’ve been talking about) and it’s gone! I suspect that it’s because I performed “clean bundles” earlier. I can still see the thumbnail on plex web because that thumbnail still exists in the Photo Transcoder folder. But I checked my phone and it’s blank! So if I clear the thumbnail cache it would be blank again on plex web. So, all this time when I thought I “fixed” it, it was still broken as soon as maintenance was performed. I just assumed it worked, but I was looking at the cached image.
I checked the database and that entry for that file that used to work is still there. So the problem, for some reason, “cleaning bundles” is deleting the thumbnails.
I don’t actually know how to fix it now because there’s no use doing the plex dance either because I’ve done that many times before and it still keeps happening.
Just for reference, what I remember doing a lot of was adding “Name” to the audio and subtitle tracks using mkvpropedit. So it’s just adding text like Chinese, Japanese, English, Forced, Dialogue, SDH, etc, to the “Name” field of the tracks. The filename stays the same, but the hash would now be different. The date modified would also be different.
I’ve tested it before. Even just changing 1 value, like making a track “forced” from 0 (disabled) to 1 (enabled), changed the hash, but the filesize and filename would be the same.
I’m just not sure how Plex determines that a file is the same file or if it’s been modified and therefore needs a “full” refresh.
