Mid-battle in the Kobold wagon adventure, I hovered over the cards in my Elf character's inventory. They highlighted my Elf on the board, making it bounce up and down as normal. After a few bounces, the Elf disappeared and became a black circle, which I assume is an underlying art asset. The character remained a black circle for 1-2 more turns, then returned to "normal" at the start of another turn. (In my 20 hours of play, this is the only occurrence I've seen and it otherwise didn't impact game play.)
Any chance you still have the full size left or caught the room number to help track down the bug in the logs?
Believe that's the second area for the Kobold wagon adventure. Is that specific enough for the room number? (Will capture the full screen next time.)