SERVO3 outputs either 1100 or 1900, nothing in-between

ArduPlane Plane 4.0
1

I’m setting up a dual-motor fixed-wing aircraft. Brand new install, just flashed the bootloader and Plane 4.0.6 on a Matek405 Wing. It more or less forces you to use SERVO1 and SERVO2 for throttles, so I’m trying to connect servos to SERVO3 and up.

I cannot understand SERVO3’s behavior. If I set it up as Elevator, Aileron or Rudder, the output is either full right or full left (1100 or 1900 us), any stick positions in the middle either “rounds” up or down to SERVO3_MIN or SERVO3_MAX. (I’m in MANUAL mode). All other SERVO* outputs work as I expect them to.

I can skip SERVO3 (the board has plenty of PWM outputs available) but it’s baffling to me that this one output behaves differently. Is there as setting I need to change to let SERVO3 behave same as other servos?

2

Several board reboots later, I cannot replicate this problem. All servo outputs are smooth and linear now.

This is even more baffling.