Bugged boss, Crowbill act1

I have found a bug in act 1.
Upon fighting the Crowbill boss there are 3 phases.
during the second phase i stun locked the boss and he stood there until his life stopped taking damage.
My character is now trapped in the arena with an immortal boss although the boss isnt doing anything .
I believe to recreate this bug you need to beat the first phase, after which the boss runs to a door, then beat the second phase. At the end of the second phase the boss takes a bell and smashes the door. If you stun the boss before he takes the bell he just stands there not doing anything. You can still damage him until eventually he stops taking damage.
You cant leave the arena and become trapped.

Confirming this is happening to me as well, during maps with boss modifier.

I have a freeze build, so like the post above, I suspect CC might have something to do with this glitch.

For me, the boss does not even get to the bell phase before becoming immortal.