Large oscillations (burping) in AUTO mode

[KobeT (Kobe)]

Hello.
When I switch the aircraft to auto mode, I am getting really large, deep oscillations (I’ve been describing them as “burping”). The auto mode was set to do a loiter at 200 feet, and manual mode is working just fine.

The burping puts the plane into a rapid decent and has caused several crashes. However, the burping doesn’t happen every time I switch to auto. In some other cases, there are smaller oscillations while in autopilot, but the plane can handle them and continues steady flight. What could be a cause for this?

Here is the flight log of the burping oscillation problem:
https://drive.google.com/drive/folders/1RGa-OKUohdgtkkSzqxyMVCWmb5t0jdzT

I don’t have a flight log for a log for the AUTO when it isn’t in this burping mode. I will try to get one and put it in the comments.

[Allister (Allister Schreiber)]

Assuming that the plane is good mechanically and that the CoG is correct, I think it’s a tuning issue, particularly on pitch. There isn’t enough flight for me to say for sure, but roll looks okay. Perhaps the pitch P-term is too high. Theres a very defined sawtooth pattern in the NavPitch and P term.