T960 Alt Hold problem

I build t960 and I want to perform autotune.
I configure loiter and althold mode and ch8 to autotune.
If I start with loiter mode the drone is flying quite well but if I switch to althold mode to perform autotune the drone suddenly turns left ( befor I switch to autotune) and I have to cancel autotune
Here Is my log.
Thx in advance