Auto takeoff (Mission) Motor Output Issue (w/ graphs)

Pixhawk 2
PX4 FW V. 1.7.3
Hexacopter X Config
S900 Frame w/ heavy payload (22ah battery and ~2.5kg / 5lb payload)

Below is data on two missions, one right after the other; first mission was successful, second was a takeoff rollover.

Both missions were under moderate wind (22mph solid, 29moh gusts), which is normal and we have plenty of fine takeoffs in this condition.

So far, we have clamped the PWM_MIN to 1200us from the default of 1075 to try and prevent the motors spinning down to far in this potential edge case.

Good Mission:
The first takeoff was great, mission success. In main outputs graph, all motors are above 1500us, even under correction. Setpoint seems to start updating 1 - 1.5 seconds after takeoff.

Bad Mission:
Motor output dip below 1500us and even close to completely off (1000us), seemingly to correct itself.
The hex flipped to the right almost immediately after spinup and mission launch command.
The setpoints don’t seem to update like they did in the first mission.

Good Flight

Bad Flight


This only happens during the first arm sequence after a power cycle. This happens on more than one frame as well.

One to two motors will visibly stutter and lag for 100-300ms. This seems like motor desync on visual, but ONLY happens during first arm.

I confirmed through hundreds of arm/power-cycle trials. It happens 70+% of the time on at least one motor.

Would love to hear any thoughts.