Just wanted to report, that it still keeps on happening to me, but you finally saw it yourself already
I'm gonna post this anyway, it might help with debugging after all:
direct link to comment of an affected thread
(I'm kinda sad, that I had to use an external service for a video, that's smaller than most images, but I can see why. before compressing it, it was 30mb in size, constant bitrate ^^)
@S77 pls tell me when you have watched it, so I can delete it then
ps: the url address bar was blacked out by chrome automatically since it was a private tab.