I got some problems with my quad. I use the 3DR ArduCopter Quad C Frame with the APM 2.6, the 3DR uBlox GPS with Compass, APC propellers 10x4.7 and Motor 850Kv
As soon as I switch to AltHold mode the copter climbs as fast as possible. I read in the common problems, that it is often caused by high vibrations. So I checked it as discribed, but I think it is not critical.
Maybe someone got some good ideas to help me.