Turret + physics behaviors = conflict?

Hi,

I am trying to create a chained worm-like creature that tries to follow and hit the player.

I need physics behavior for hinges and turret behavior for the object to look at the player. Lastly, I need bullet behavior for moving forward.

Before creating hinges and such, I need the head first. So I have 3 behaviors on and test it. Somehow, here comes trouble, it seems that the turret behavior conflicts with physics behavior. The object moves with a very high angular velocity (it moves round and round), when the object "acquire target".

Is there a way to fix this? I just want a worm-like object that consists of a few chains (hinged objects) that follow the player.

OK, I think I now understand the root of trouble:

Here's my cap: dropbox.com/s/uggff4bwrz6b4e6/bulletPhysicsTurretTest.cap

It seems that Physics+Turret+Bullet behavior will have a bug if I change the hotspot of snakeHead to somewhere else beside the center of the image. Try it with the cap above.

I see that Physics behavior seems to prefer Sprite to have hotspot in the middle.

Also, if I remove physics behavior out, hotspot can be anywhere.

Also, it seems that physics behavior somehow "hiddenly" add acceleration to the sprite on its own. Perhaps there are some contradicting logic inside the behaviors?