Gimbal Yaw error when Arducopter boots

Hi all, I’m hoping somoen can help me fix an issue I’v had for a while with gimbal heading.

I’m flying a modified Tarot T690 with a Cube orange and an own design gimbal. Connection is via Telemetry 2 on the FC. I’m running ArduCopter 4.3.2 at the moment
The gimbal works perfectly when not connected to the FC, but once it is connected the gimbal heading seems to drift over time.

I’ve tested this by powering up the gimbal, then once the FC boots I can seen the heading drifts immediately. The short clip below shows the issue - you can see the heading about 60 degrees out from straight ahead, but this tends to vary between flights and sometimes over time. (the twitching is due to travel limits with some mods I am adding to the gimbal)

I’ve trawled the info and as far as I can tell everything is set up correctly so I’m a bit stumped now with what I can do to help this. My paramters as I am flying at the moment are below.
20230107.txt (29.5 KB)

I plan on adding encoders to the gimbal shortly which will hopefully help performance, but as this seems to only happen once the FC boots up it points to the something in the setup that I may have missed.

Any advice you can give would be greatly appreaciated.

I’ve just realised I hadn’t mentioned the gimbal controller. I’m using the Basecam Tiny controller.

I’ve gone to fly this morning and have ahd the same issue gain, but this time I’m out by a full 90 degrees in yaw angle. I’m completely stumped as to what may be causing this as when there is no data coming from the FC the gimbal maintains it’s heading. I don’t really want to go back to RC targeting though as that would mean losing the nice level horizon I have when yawing.