At the point where you defend the mage, one of the shadows runs through the barrier and won't come back.
Happened on elite. GM killed it and another one did it on the second wave. GM had to kill it too. After completing, I went back and ran the chain on hard...
Happened again on hard.
I'm running with an owlbear and a level 17 cleric hire.
Bug report has been submitted.
Who else has had this happen?