I’m not electrical minded as some of you know

I’m hoping this is a simple fix, when I engage reverse one of the following happens:-
The passenger door mirror dips but jerks on its way down as if it’s sticking
When it goes down it then sometimes does not go back up when I go into drive
Sometimes it does not dip at all
Anyone any ideas

Is it a simple poor connection somewhere,
Motor in the motor
no idea where to start looking on this one

Cheers in advance for any help