New build-Pixhawk X quad - one motor starts at 50% during motor test

Hi all, need your wisdom …
New build (my first), X quad copter, 4 3508-700KV motors, SimonK 30A ESC’s.
I run ESC calibration through Mission Planner (no RC was connected).
Then I went to motor test.
3 motors respond well to any throttle, one seemed not to respond at all.
I disconnected this motor and connected it to one of the other ESC’s on the drone and it works fine. That lead me to assume something is wrong with the ESC.
Tested the “faulty” ESC + motor via a receiver and an RC - works fine, therefore the ESC and the motor are not the problem.
Connected it again to the Pixhawk and same. Only now I decided to re-test with 50% throttle and… It works.
Summary: one out of four ESC’s respond to a motor test on MP only at and above 50%.
Any idea?


OK all, just though it might be a calibration issue (calibration through MP). So I disconnected the non working motor from Pix, connected it to a receiver and an RC, calibrated it (no battery -> full throttle -> battery connect -> throttle down to minimum) and then reconnected the motor to Pix. Now it responds to motor test !!

Conclusion: Calibrating through MP, without an RC, seems to be problematic.