Look at the top yaw shaft first. Make sure the grub screw sits against the flat side. Also check that the yaw shaft isn't bent. If its bent, it would put pressure on the bearing case and not let it rest properly. Looking at your video, it looks like it sits to one side when there is no power and it slaps to the sides when there is power. This will cause it to be unbalanced on initialisation. Another thing you can do is swap the axis boards around. The roll axis board shares the same as the tilt axis (DJI used the same boards in the H3-3D for the tilt axis). If that all fails, look at each of the axis boards and pop open the potentiometers by using your finger nails. Inspect the Omega rings and make sure there are no cracks.