I'm having the same problem, but throughout the game. Characters just lock down and stop doing anything. The temporary solution I found is selecting the character and hitting the jump button (I do play on PC, so it might not work for you).
It doesn't always work, with results in currently me playing the Descent with only one character. Blackwall draws fire, locks, dies. Cas locks, dies. Sera doesn't even enter combat, is locked, and usually dies. It basically renders huge combats unplayable, or requires a lot of reloads.
It is a VERY annoying thing. I hope it can be fixed in a future patch.
I also have this problem. I'm on PC. I heard lunge and slash was bugged, so I disabled that for Cassandra and Blackwall. My biggest issue is the Bull because this pt I take him everywhere.
BTW, this is not location specific. It seems to happen anywhere.
