We've made our way through the mines and when we go to leave via the clicky mirror we end up back in Luculla Forest in combat with two trolls. Consistently, though, one of the party members immediately "drops out of combat" (their portrait disappears from the set of "who goes next" icons at the top) even though they're right there. A few people may get to take their turn (based on initiative order) and then it inevitably ends up "waiting" indefinitely where the out-of-combat person can act, even attack once or twice as if they were in combat, but then nothing else has any effect -- as if they'd used up their points and it was someone else's turn, but the game won't move on to the next person. The out-of-combat person can still move around and perform attacks that do nothing, but nobody else can do anything, the mobs do nothing any more at that point, everything is stuck because of the one character that's in combat, but not in combat.
We've tried reloading multiple times, dismissing the hires and exiting with just the two main characters, swapping out who has control of which character, etc. but in all cases we end up with one character getting dropped out of the fight and messing up the game.
If it were at any other point we'd try pyramiding around the issue, or something else, but since it's in leaving the mines, there are no other options for getting out that we know of.