Strange behaviour PWM commands via QGroundControl Motors Setup?

We are experiencing some issues with the Motors Setup in QGroundControl.

  • When using the sliders to manually test motor control and direction, the motor only briefly spins instead of the 3 seconds that the slider is up.
  • When I change the slider of a different motor within that 3 second time frame, the motor will spin again briefly.
  • When I try spinning all motors using the “All” slider, all motors spin briefly but error messages appear saying: “Unable to send command: Waiting on previous response to same command”.
  • We have probed the port with a scope and it also only receives the PWM pulse briefly, so we belief the problem to be on the software side.

Does anyone recognize this issue and/or can point us to a solution?

We are using the Pixhawk 4 with a HolyBro PM07-v2.2 and the EMAX MT2216-810KV motors. The motors are wired tot the M1-4 on the PM07 and we are using the I/O PWM OUT on the Pixhawk. Running the ESC calibration works, and it has set the PWM_MIN at 1075 us and PWM_MAX at 1950 us.