Unspotted characters leave turn based mode when another character starts combat - eviltoast

Is this happening to anyone else? I’ll set up a clever ambush, load everyone up with buffs, and start a surprise round.

When I finish up the turn of the character that started the fight I discover that turn based mode has auto canceled for my other characters, all my buffs are worn off, everyone is out of position because of the group mode and someone is dead because they were standing in poison! Arrrg!

Is there a way to make turn based mode stay on? Or is this a known bug?