First one seems to be just a portrait error, rather minor visual bug.
The second one is likely due to the fact that Mirabel is not meant to be acquired that early at all, so the game does not remove her from your party when the flashback starts and therefore makes her the "lead" party member. Sounds like a visual bug, but it's still a thing I have to fix regardless at some point. I assume after the flashback ends everything is back to normal and it has no lasting consequences?