Hi, i think i had the same problem, reported at Copter-3.4-rc4 available for beta testing
My quest started to climb right after moving the stick to around 60% in AltHold. Then I had to bring back in manual, with weird attitude changes.
Also after a few seconds of being armed, i get bad AHRS message, event after recalibrating acc/compass.
I just rebuilt the rc3, and will check hopefully today after work.