So I just made my way down to the mimics. And instead of attempting to open the chest, I cast Cloud of Dagger's on them. Instead of initiating combat, it locked the character and the targeted chest into some kind of dialoge bug. It shows the black / white chat bubble over my character's head and the chests head. When the cloud of dagger's ran out of turns, it dissipated and the chat bubbles remained. And now I appear to be stuck. I then attacked with my rogue (Astarion), and used a ranged attack. The mimic's popped to life, but it also put the entire group with chat bubbles over their heads. And it appears to have locked them all in this state.
After a few minutes. I hit the spacebar to "end the turn" while locked in some weird chat bubble state... And combat began properly.