After several well-running AQ copters I now have an AQ with a strange behaviour. The copter suddenly drops in manual mode and forces me to catch it with high throttle values. As you can see from the logfile, throttle factor isn't yet perfect but this shouldn't affect hovering in manual mode.
Vibrations are not the very lowest but not too boad for such big props. I have had copters with much more vibrations and that only led to high mot_pitch/mot_roll outputs and in very bad cases the copter was shaking a little. This symptom of sudden dropping is new to me.
Motors are Tiger MN3510-15 with Tiger 15x5" CF props. Batteries are 2x APC 4S 4500mAh. AUW of the copter is 3.250g.
Logfile: