Throttle fluctuates to 0% and back on mode change

ArduPlane Plane 4.3
1

I have a Tilt rotor quadplane here, Ardupilot 4.3.1

Aircraft transitions and flies correctly in FBWA. However, upon changing to Auto, (or presumably any other mode with auto throttle) in some fraction of a second the throttle output plummets to 0% before returning to a controlled value, which is very difficult for the motors and ESCs. This is despite the default 100% setting of the throttle slew rate.

ThrottleError
ThrottleError1279×618 67.7 KB

Is this a known behavior? Is there any way to prevent this?

Thank You

2

Please send the log in here.

3

Here the log

After the blip it was dead stick because the ESCs desynced

Thanks