Hi SevenAteNein,
Welcome to the forums and thanks for reporting the bug. Does the freezing happen in every boss battle, and is it on the boss's turn? There seems to be an issue around paths being blocked by fire, might be worth keeping an eye out for this as a common factor. I'll play a few boss battles and see if can recreate the issues.
You're likely correct on the cause, it sounds like the AI either couldn't find an order, or has chosen an order it cannot complete.
I'm looking into the issue with enemies not being incapacitated at the minute, have a save for it, so hopefully will be able to recreate the issue quickly.