Flight test -Altitude mode - strange behaviour

I try to fly in ALT mode and after some time copter start climbing up, but I have throttle all way down.
It is very visible in logs LPSP.Z star rising around 11:44:52
but throttle channel RC.C0 is at same time down.

Before flight a saw ATLCTR rejected error, but I way until is mode switch ro ALTCTR OK. What can cause this rejection?

Flight with pixracer from AUAV and stable PX4 FW

Thanks for any advice what can happens

Hello. Have you found the problem? I met the same strange behavior recently. Thank you