It may be that this odd action has been experienced by other Q owners. I was flying at a place known as Sunset Rock. It is a high west facing overlook point popular as a vantage point. It has a small parking area aside from the road, it is accessed by a single lane that loops around a large rock standing about 65' high at the roadside. As I returned to land beside my vehicle the bird cleared the chasm and flew above the parking area and I reduced the speed to turtle mode, at the same moment it began to sashay, that is swing crazily rocking side to side violently, so badly I feared it was going to come down on it's side. Just as suddenly it leveled off and climbed vertically extremely fast despite me holding the left control stick down. it climbed to about 55' before hovering for perhaps two or three seconds, long enough for me to think I had lost it and was about too see it fly off over the distant horizon, then just as suddenly it responded and descended to land without a problem. What happened! I convince myself it was an updraught or something but there was barely two mph of wind. I am extremely puzzled. Anyone else experienced such odd behaviour?