Bugged out for me too. Tried elite with a pug - lev 20 monk, lev 20 wizzie, my lev 20 rogue and lev 20 FvS hireling. Not a bad group, but the hireling died a few times. Was actually quite fun, despite the spinner being immune to damage most of the time - we need more pots.
Problem was the monk was too good and I forgot to warn the party about doing the wards too quickly. There was never a shortage of little blue spiders and so he actually managed to get all the wards lit before the orange spiders even got summoned. We got imprisonned and everything died. No orange spiders, so we were okay.
Eventually the prison ran out - I presume it's timed which is why people are trapped in it after the cutscene - and we ran around a little, but there was nothing we could do.