Strange bug with one of my SEMPQ units

For our TC, we modified the Ancient Protector to be a human-built structure, with the same model stats. Most of the time, the peasant can build it properly. However, randomly during games the peasant will run up to build the structure, and then suddenly will stop, refusing to build it. For the rest of the game you get the same result. I have a feeling looking at the failed build attempts that this has something to do with the collision detection of the model, as the wisp "builds" the AP by sacficing itself, with the AP replacing its spot on the map. However, the peasant actually builds it from a distance, so possibly that's causing the bug. Does anyone have any insight as to what it causing this annoying and costly bug, as well as how to fix it?

I take it no one's run into this sort of bug before?

it may be that the human towers do not have an attack animation, and the game sees this, so it goes retarded. umm... try modifying a human building instead of modifying the ancient protector.

at the moment... it's all i can think of.

The thing is, I already thought of that. The AP is needed since they unit we are making ("MAC II Monster Destroid") needs to be able to "uproot" and walk around just like that unit can. However, I already tried copying that unit's stats onto the Human Watch Tower, using the AP Model +stats. I still get the same result. I'm guessing the problem is the AP model itself, so hopefully that means that when we replace the model with our new one the bug will go away.