One of the UR seems to reset every time I reload the game. I don't really know how to say which one since the artist name isn't displayable, but it's the one where they raise their skirt and they wear a pink/purple outfit. It shows up toward the end of the list.
From what I can tell, it's the only one that doesn't save the fact that I've gotten it already, but I haven't finished collecting the URs or legendaries yet, so I can't say for certain.
I also noticed the Seia legendary struggles playing more than the others.