Altitude changes while hovering

[Chuck Young]

So I have noticed a couple times the P3P going up and down while hovering, happen both on manual takeoff and auto takeoff. Last night on auto takeoff it simply started climbing out, at about 40 feet above where it auto took-off I commanded it to come back down and immediately landed it. I cycled power on the P3P and took right back off without any problems at all, rock solid. Another time it started going up and down on hover, I ignored it and finished the 10 minute flight without incident. When it returned it hovered steady.