I thought it was just me, but this seems to occur only in Thaumanova Reactor story mode instance, and other players in my party are experiencing the same thing.
Sometimes the instance would stall for 2 seconds, and it’s very inconvenient when fighting the Thaumanova Anomaly boss. The lag hits and then I’m suddenly teleported dead in the middle of the platform, along with everyone else.
At least the dialog between Kiel and Dessa played normally and we were granted the second chest, but the party shouldn’t have to suffer due to sporadic lag in this story mode.