[bagofcrap24]

This entire series has been fine until updating this evening. Since updating all 3 episodes so far have the issue so I would say your right that it's an issue with the updated libass.
It's hard to reproduce because it doesn't happen every time. If it bugs. I skip back and watch again. It doesn't bug the next time.

EDIT: happening all over the place. sometimes repeatable. sometimes not.
for anyone else, this is what it looks like.