I made a plane to do a experiment ,and i found a bug.
This is my plane

while it is flying,it yaw swing very intense.

and its amplitude does not decrease
But When I slow down the time, its amplitude decrease normally.
I don't know why does this happen.
And there's another situation:

I put a rotator between the aircraft and the air brake.And the amplitude decrease soon.This is what it should be.
I know if I put a vertical wing,there's no problem,but I want to know why the amplitude can't decrease in the GIF.
I think its a bug.How do you think this is caused?