I found that several of my images that I loaded were side-ways so I had to rotate them, but when I went to rescan them, the original thumbnails were still there. How to I get rid of the bad ones and rescan to get new ones?
I think that “Refresh Metadata” will fix it. No promises, I don’t have a big photo library, so my experience is somewhat limited… That command/option usually fixes up videos and music, though… 
If you have a bunch, refresh metadata on the whole library might be quicker, although I don’t know what it will do to any manual edits you may have made to the photos.
my bad, you can’t refresh metadata on individual photos. (I don’t have that option) Maybe wait for a better answer before you do it on the whole library.
Thanks. I am going to let it run overnight anyway.
Well, that did not work. The thumbnails are still there. So it looks like I still need help.
Since no one else has jumped in… Maybe try the “nuclear” option - “The Plex Dance” It’s the official unofficial way of clearing all of the bad metadata out of your database.
The article is a little out-dated. You can find the “Clean Bundles” command in Plex Web under Settings → Manage–>Troubleshooting. I would probably only move the files with the bad thumbnail images, but that’s up to you.
Here is a work around. I renamed one folder and rescanned the library. This eliminated the folder thumbnails that were wrong and created ones that were oriented correctly. Then, I renamed the folder back to what it was and everything is correct.
But, Plex should have a better way to do this. Like finding the folder that holds the thumbnails and remove them. And then regenerate.
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I still need some help. I have discovered that renaming a folder to something else does get the correct images displayed and in some cases, the thumbnails also get redone, BUT, if I rename the folder back to what I really want it to be titled, the corrupt thumbnails one back.
PLEASE!!!
Where are the thumbnails stored?
How do I get rid of them and have them create NEW ones from the non-corrupt images?
PLEASE!!!
HELP!!!
This procedure might help you → Reset all manual poster selections in a library at once or unlock other metadata fields
It will reset the locked fields for thumbs and can be done at various levels including movie, show, season and episode depending on your needs.
Might be worth a try as it should reset the fields for the thumbs and then doing a force metadata refresh should get plex to download new ones. It would however blow away any your manually selected as it resets the locked status might worth a look at.
This is just plain BAD. I actually went ahead and deleted the library. I moved the image’s folder to somewhere else. I added a new library something else and then it scanned.
THE CORRUPT THUMBNAILS ARE STILL THERE!!!
I believe that Plex is refusing to rescan for a thumbnail based on the full image as it still has memory of the file name of the full image and match it to something in its memory.
I have tried to use the Delete Thumbnails with NO success.
NOW WHAT DO I DO TO GET RID OF THESE?
I was looking through my Synology System to see if I could find them and found this…
There are a LOT of these folders that seem to contain “pmm” and “jpg” files that are super small and then I look at these, they seem to be a thumbnail of full image. Would just be possible to remove all of these jpgs and then run a scan? When I looked at the highlighted image, I was able to find its full image…
Have a look at this thread for context Cache/PhotoTranscoder Folder Size Sanity Check
That cache can be safely deleted and plex will recreate it again as needed.
So this is NOT where Plex is storing the thumbnails?
I am beginning to get desperate on this.
I’m sorry, I guess your talking about photo library and not thumbnails from movies, shows or episodes.
Ignore all I said about and let’s wait for someone from plex to respond.
Right. I am storing movies and music as well, but my primary goal is to use. Plex with images for the family to enjoy and contribute. I have over ÂĽ million images so far.
I’m curious- did you actually try the complete “Plex Dance” I mentioned previously for the library.
Plex will stubbornly hold onto bad metadata and posters, when you remove items from your libraries (any kind, not just photos) Although it will remove the metadata eventually as part of scheduled tasks, that could be a week depending on when you removed the items.
The only real way to get rid of it immediately is with the dance, in the exact order, and completely. Particularly the “Clean Bundles” step to clear out the metadata.
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First - how do you empty the trash and then secondly, where is “clean bundle”? There is NO option for that.
In your file system, move all your photos out of the library directory.
In the web interface, hover over the library, select the three dots, choose Manage Library, then Empty Trash.
Then, go to your PMS settings, go down to Troubleshooting. This is where you will find Clean Bundles.
Move your photos back into the library folder, then go back to Plex and rescan the library.
SUPER SUPER SUPER!!!
That worked. Thank you very much!
Well, say again. Opps. Not ALL Fixed. I read some more on the troubleshooting actions and decided to try something even more intense.
I removed the entire folder that contained 1979 photos. Because these were initially titled 1979-Fix, I wondered it Plex was still hanging onto some thumbnails somehow. So, when I moved if off the server, I renamed it back to 1979 since I KNEW that the full images were just fine.
Then I Emptied the Trash.
Next I Cleaned the Bundles.
Next I “Optimized The Database” - It said here that it was “especially useful when you’ve added or REMOVED a large amount of Media from the library”.
Then I Emptied the Trash again and Cleaned the bundles and Optimized the Database.
Then I brought the new “1979” folder back onto the server and rescanned the library.
THIS TIME ALL OF THE THUMBNAILS WERE GOOD!!!
I think that maybe the volume of images may need a little more intense cleaning.
… not sure if you took the step BEFORE these two steps, which is scan library files (after you’ve moved them). That will make sure the Plex knows the files are missing, and not just unavailable at the moment… It’s important to do all of the steps, or the dance might not work properly. 
