If you have not checked this, try: the lower rotor head pins can be sheared off and hard to detect. If you remove the lower blades, you will see if the plastic pins that the blades slide on to are broken.

I dunno, just a thought if you have tried everything else.

* Also, the 4 in 1 needs to be upright and straight, so it seems. For the gyro, I guess. I have laid mine sideways before and it made the heli act weird.