Help. The aircraft does not hold altitude in auto mode

Hi. I would like to share a strange problem that I have been dealing with for a while. When my plane is in auto mode, it starts to lose altitude automaticallyю.
I have a Cube Orange, firmware ArduPlane 4.1.0 stab.
Here’s a copy of the full log:
Help to understand the reason. Thanks

Your flight seems to be a lot of turning so try: Increase PTCH2SRV_RLL in increments of .05.

Thanks for the answer. Many turns is a manual flight to test the aircraft’s aerodynamics. The main problem is that in automatic mode it takes off and gains altitude, after which it flies to WP. Altitude control stops working in this mode.

Therefore, we switch to manual mode for further testing. Brief flight video

Could it be that you have TERRAIN_FOLLOW enabled? In this case, the automatic height control modes would try to maintain the height above the ground at the moment the mode was activated.

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This mode is enabled. But even in Guided mode, the aircraft does not respond when indicating a change in altitude. Thanks for the answer.

Thanks everyone. The problem was solved by switching to firmware 4.1.2 stab.