I received a replaced Mavic Air (which I got as a warranty replacement) and I noticed that the gimbal that is pointed all the way downward jerks/moves up a little bit during breaking and does not return to the 100% downward position. I need to readjust it with the controller to point downward again. I don't think it's normal behaviour and it ruins the end of the footage. Strange as the original Mavic Air that I bought didn't have that issue What can be done to fix the issue? It is actually a second replacement and the aircraft still have issues. Additionally, now my warranty is over...
I also noticed a tiny jerk when the gimbal points more up in the beginning but it is less visible in the footage. It is as if the gimbal was loose a little bit perhaps? Hmm.
If I slow down the drone smoothly the gimbal doesn't jerk - so maybe that's the solution.... but did anyone else experience such behaviour?

The gimbal involuntary movement is recorded in the DJI GO 4 app as well in the flight records. The dot in the gimbal scale on the right just moves one millimetre up.

I would first turn the drone off and carefully check by hand that you have smooth movement of the gimbal on all 3 axis through it's full range.  Sometimes if you have taken-off or landed on gravel or dirt, particles can fly up and lodge in the gimbal preventing smooth movement.

Thanks for a reply
I start and land always on a landing pad. It was just the second flight since the drone came as a replacement so it's as clean as can be... (and it looks as if it's brand new).