I thought I experienced the same thing. On further experimentation, however, I found that the game was removing 2 of my characters from Turn Based Mode, shortly after the combat started. Once it did that, the spellcaster's concentration timed out in real-time (as he was no longer in turn-based mode). Why the game is doing this, and how to prevent it is TBD.
Last edited by TDeacon; 09/09/23 07:02 PM. Reason: New information