Copter in AltHold mode unwanted engine spin-up and crash


I was testing a quad indoors using Marvelmind beacons for position, but trying a flight in AltHold mode.
After arming the copter and rising the throttle (not even to mid position), suddenly motor 1 spin up really fast, pulling the quad to the side and crashing into the wall.
Checking the log, I see no intentional attitude change from the autopilot, still it sent rising signal values to the RCOUT1 channel.

What could have been the issue here I’m not seeing?

00000086.BIN (656.9 KB)

Hi @Zoltan_Szoke
in your log after initializing firmware you can see inav error and lane change mesage

you are using EKF3 that is still in beta , maybe you were faced an EKF3 bug.

but totally what will cause lane change :

  • Large change in IMU bias, common in long flights with low-grade sensors

  • Two different barometers, significant drift in one due to high temperature

  • High magnetic interference, different rates of coping in magnetometers

  • Two GPS modules, one drifting badly in height

in your log there is large diffidence between your mags.
but it must not affect althold mode and stabilization at all

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Thank you for the information