Uploaded Vimeo thumbnail fails

I made a small edit to the existing thumbnail and re-uploaded, and it fails like this. The small preview works, but the image doesn't show when saving. I made sure it is the exact same size in pixels as the old one.

Anyone know what to do? Does it have to be a super specific size or something? It should not really matter, since I used the same size, but I have got it to work by trial and error and trying many different sizes, but can't seem to find a pattern.