The disappearance of character portraits and backgrounds

Yesterday, it started happening to me: the portrait pictures of my characters gradually disappeared, not just for my own characters but also for my players' characters. Now none of my characters have a working profile picture anymore. It's even stranger with the backgrounds, as some characters still have them while others are completely white. The only things left are a picture icon and "Character portrait." The information on the character sheet is still there, and dice rolls still work, but something about this is odd. Has anyone else experienced this?

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See Portraits not loading  on the long long history on this particular bug, and work arounds for avoiding it.