Maybe this will help.
1) Double check the number of poles configured for the yaw motor.
2) Move the pan motor wires away from possible sources of emi such as battery or battery regulator.
Switching/digital volt regulators produce emi as well as possible voltage supply ripples.
Make sure the BG controller is not getting supply power from two difference sources, i.e., should not come in from servo wires if all 3 wires are connected from the FC which is not good.
3) Re-calibrate the yaw IMU gyros..... they drift a lot......
other reference info.
Fit a ferrite ring around the motors outputs on the board and the I2C cable still right out of the board. Also, use a LC filter (Power Noise Filter) if you feed the gimbal right out from the main lipos.
I2C errors are worse when the sensor cable is running along aluminum parts or close to the motors / motor wires. Make sure to route it not too close to wires that emit RF noise.
I now got everything to work EXCEPT the pan axis... after i turn on the gimbal (wait 10 seconds) the pan axis moves back and forth almost violently. It travels about 2 inches both sides...
This was working completely fine before... so not sure what happen...
SOMETIMES i get a I2C error of motor skipping or something like that (haven't seen that error since yesterday).