my bird is a 76 cm Hexa with the APM 2.0. It has 1000 kv motors with 10.5" props. It flies great in stabilized mode but when I switch to altitude hold it slowly descends and then shoots up a what sounds like full throttle.
I am using sonar and I believe that I have my vibrations well within tollerance.
I have been trying to get it to work properly by changing the throttle accel settings but to no avail.
I have included a log file and a couple of pics of my bird. It's been a build going on for about a year but im still to nervous to put on my FPV gear.
It's outfitted for night flying too.
just to go to the interesting thing, i get nice altitude hold (soft 3.0 rc6) for a while, ad it goes full throttle at random moment. I had 3 min hold and throttle up then and also a 7 min alt hold before it tried to fly away...