Immediately after arm, motor RPM increases even though no takeoff operation is performed

In Loiter mode, after arming operation from RC, the RPM of the motor started to increase even though no throttle rise operation was performed.
Normally, after arming, the motor should rotate at the pwm set in MOT_SPIN_IDLE, and the motor RPM should not increase until takeoff operation is performed.

Can you please help me find out why this event occurred?

The logs can be found at the following link

My drone has a custom firmware installed based on Copter-4.1.0.

Flight controller:CubeOrange
Battery:12 cells
Propeller: 32inch
Motor: KV100

I don’t think so.

Can’t get help because it’s custom firmware?

I would like to get some clues.

All thoughts are appreciated.

I will be grateful for any help you can provide.

Yes and it’s based on old firmware. How would anyone know it’s in Loiter looking at that log?

Good luck.