Running SITL with gimbal (-M) constantly closes connection

I’m running the following SITL script, after following instrcution at (note: due to missing params RC6_FUNCTION, RC7_FUNCITON, I followed this link - What replaces RCx_FUNCTION?, and switched to SERVO06_FUNCTION and SERVO7_FUNCTION).

./tools/autotest/ -M -v ArduCopter --out= --use-dir copter1 -I 1

Connection with either MissionPlanner or QGC shows the comm link is constantly breaking. Is there a known issue ? BTW, running without “-M” works perfectly fine, but without gimbal…