Originally Posted by theothercliff
One of the problems with any helicopter is rapid vertical decent. The heli gets caught in it's own downwash, a little off to one side and it tilts a lot. It will always be off to one side.
Adjust your P gain (aileron / elevator = roll / pitch) up or down to see what makes it better. I am guessing that you need to increase your P gain, but if you increase it too much, you will get oscillation. The way to increase it more without oscillation is to flash your ESC's with SimonK.
If you see oscillations in fast forward flight (or in wind) you need to reduce the P gain.
Here is a video about tuning your gains:
I posted after you and didn't see. My ESCs are flashed already. And I only see oscillation when it comes down fast.