I have an obnoxious issue (as well as a friend) with the Plex Web App, which started happening earlier this year seemingly limited to fields in the "General" and "Tags" sections of movie library metadata. I'm currently working around it somewhat reliably but that makes the issue no less aggravating.
My process for now is to, say, move the (new) file "From Russia With Love (1963).mkv" to my storage device, "Scan Library Files" (for just the one library), and once it finishes successfully matching and processing, I click the pencil icon in the corner of the movie's poster (from the home screen), capitalize a word in the title (lock icon goes orange as expected), click over to Tags and add/remove a thing or two (lock icon goes orange as expected), choose a poster and a background, click Save, and all is well.
However, when I immediately click the edit pencil again, while my changes are still present, the lock icon is no longer orange, meaning the next time that data is refreshed (by the butler or otherwise), the changes to the title and the tags will be lost/reverted (poster and background changes always remain, without issue). This tells me it's likely an issue with the lock feature, as if I simply click the lock icon next to the fields I've modified when I view them that second time, and click Save a second time, everything finally sticks. But that's of course very silly and very time consuming, and needless to say, I'd love to go back to everything working/saving as it should. Thoughts?
Side Note: Every time I scan a library, it first auto-refreshes the last movie that I viewed the full/details page for, instantly eliminating the changes I've made if I haven't re-clicked the lock icons as described above. Likely a separate issue (auto-refreshing the last viewed item on library scan), but it adds to the frustration of the aforementioned issue, so I figured I'd mention it in case it helps in any way.