What determines whether the chicken moves while ruptured or not? I have polymorphed Rangers, Mages, Warriors, and a whole bunch of monsters and there has been zero consistency regarding whether or not the chicken moves. Sometimes they don't move while they're sitting in the open, sometimes they move through 3 attacks of opportunity through fire.

My friend and I were unable to find cases where it 100% moved or 100% did not move even in GM mode.

Is this bugged?