I got Praetorium in Main Scenario Roulette, and things were proceeding as normal until we got to the part where you fight Gaius van Baelsar in the elevator. The pre-battle cutscene plays, but during Gaius's speech I see in the chat log that the battle has somehow already commenced and the room has sealed.

Apparently, a few members of our party were able to fight and defeat Gaius while the rest of us were still in the cutscene. This also happened for the very next boss fight, as well.

At first I suspected the players were up to some filthy shenanigans, but then one of them seemed confused and said something like "There is only three of us?" Luckily I don't think any of us were first-timers so nobody's story experience was ruined.

This occurred yesterday (Sept. 3) at 4:43pm EST (at least that's what my screenshot image properties say). If it helps, my character is Friel Wyndor on Siren.