Bad loiter stability if DYS gimbal attached

Hi everyone

Here is the situation. My IRIS flies very well without the long legs and the DYS 3 axis gimbal attached. It has been updated with Arducopter 3.1.4, R/C, accelerometer and compas calibrations all done after the upgrade. If I put the IRIS in Loiter mode I have a very steady position and altitude hold on that config.

When I attach the long legs and DYS gimbal (and gopro Hero3 Black+) I have quite another situation : loiter is very bad : the quad moves several meters away from its spot. The GoPro wifi is off, and the IRIS is configured with the “3DR IRIS and Tarrot gimbal” parameters via MP.

I have no clue what’s causing this issue. This is my first arducopter machine so no real experience yet in analyzing the logs. You can find attached the tlog. The datafash log can be downloaded from here : … -55-01.log

Any help and advise would be greatly appreciated !

Anyone ?