GrognardsFromHell
Prefer full attack + Stunning Fist
It seems that if you have the game set to prefer full attacks, then stunning fist will automatically initiate a full attack if possible. Most other special attacks don't do this; they're usable within a full attack, but selecting them without first initiating a full attack will use them as a single attack.
This wouldn't be a big problem as a default, but there doesn't seem to be a way to not do the full attack.
Err, are you sure it's related to that setting? I just tested and it did the same with prefer 5' step turned off.
Hmm, I don't actually remember if I tested with it off. It's possible I just presumed that the setting was meaningful.
Hah. Okay then. Sorry for the wild goose chase.
Edit: oh, speaking of vanilla stunning fist bugs, should I try to fix the fact that the effect expires when initiative wraps around? Most other stuff counts on the affected character's turn, which can be slightly too long, but it ensures that the target is affected on one of their turns.
Interestingly, on further study, the ticker for stun is trying to do the right thing. It stores the monk's initiative in one of the arguments, and then on each X->Y change in initiative, it does some checks. But the case where the initiative wraps around from a low number to a high number must be faulty.