I have recently noticed that most of my movies info page are missing actors picture, showing generic place holder instead.
No library scans or library refresh metadata/look for missing data seems to do anything.
The only workaround I have found is to manually redownload the actor's pic.
An example
So I click on first generic tile (Peter Capaldi here)
What do you know, Emby does have a pic for this actor, yet shows a generic tile instead in media info.
The
I've had similar (or same?) issue as well, best described as an "empty image" placeholder on top of actor image, not the usual "missing image" one but plain, dark gray/blackish image instead. And same like you, went to sort it actor by actor - which got tedious VERY quickly, so I just gave up and updated few images every now and then when need arose (or my OCD went ballistic). However, as far as I can tell, @mickle026's relatively recent plugin:
actually sorted those out, at least I didn't