DJI Phantom 3 Standard camera gimbal failure.

Rebuilding a Phantom 3 Standard for a friend. It apparently hit a tree that leap out in front of it. Usual Yaw arm bracket and flex cable breakage which I have repaired before. (yeah, he’s not a great pilot). Now when it starts, the camera gimbals are pretty erratic and it doesn’t stabilise. It is like it is trying to drive into position but can’t find it. I have watch various Youtube videos to see if I have slipped up somewhere but I think I have it right. At first I used an aftermarket flex cable but I have changed it again for an original DJI version. I’ve checked multiple times that the flat on the Roll motor is parallel to the top of the camera housing. All motors turn freely, no binding.