When throttle is cut, plane is waving (jumpy) in pitch - PID related?

My Mini Talon flies quite good when I use some (non-zero) throttle.
If I cut the throttle to zero, plane starts wave (sway) in the pitch axis. It has nothing to do with real thrust or speed but is caused literally by “zero throttle” condition.

Even if the TH is so low, that engine hasn’t started yet or has no real thrust, problem is not there.

Please look at the short video here, it’s visible also in the this log at around 23:03:10
Waves are visible also in this picture:

For flight with non-zero throttle is PID controller reasonably adjusted.
I guess there could be some advanced parameter causing different behaviour without throttle, but I can’t find which. I suspect that I-term behaviour changes when throttle is zero, but can’t find details. Can someone advise?
Thanks! Roman