Problem: BK motor wobbles up and down.
Check: look at screws on the side of the motor.
These two knobs need lock
and all the screws here need lock
Solution: If the two knobs are loosened you can move to 45 or 90 degree. The knobs nuts run in long slots that allow movement to 90 degree. If you have just few degrees movement the 16 screws that are loose.