Indeed there is a bug with the update of the thumbnail.
The good news is that I found exactly where and why, and it is very easy to fix.
The bug exists since several months, but the bright side is that I can easily find all those which were not updated: the new thumbnail is still laying around. I just have to write a small script that will replace the forgotten thumbnails, by checking if the pic wasn't updated again by an admin in the meantime (otherwise it will just delete the useless new thumbnail).
I'll already fix today the code for future picture replacements, and for the previous ones I'll try to write a script to clean that in the next days.

That's the latest example: https://www.imcdb.org/movie_83086-Sista-budet.html

Replacements have been validated but I can still see the old ones unless I click and open each page.

I fixed yesterday's bug more properly, I hope that this time all is fine.

Apparently, it seems that the comment has been updated at the server, but the latency tends to send a response to the client end usually slower. I usually wait until the page updates. But then, some people who doesn't understand the quirk of the request/acknowledge of the services

Until yesterday I suppose some clicked again because it took too much time to their taste to respond, but since then normally these slow downs should be fixed, aren't they?

There has been a case with a picture from MisterZ recently, but I don't know the cause.
Was it also from him? Which movie?
or more random?
Replaced by an admin or by someone else with validation?

We seem to be getting a steady trickle of double comments from several assorted contributors, as though it stuck the first time so they pressed the button again. Have noticed this as I've been deleting the first of the repeats fairly often over the last few days. Some have been simple one-liners, others when they've quoted a previous comment, but haven't noticed a definite pattern.

Is it just me or the replacement pictures don't appear in thumbnails even after refreshing the page?

Thanks

Crap I fixed a bug and created a new one
I've put back the old version of the edit page, I'll fix that properly later.