Wing Mirrors: Working separately

I have a 2007 S/C Range Rover, since it has been bought from new it has been returned to the dealer to have the same fault repaired 4 times: When I press the button to fold the wing mirrors in, one goes in/the other says out; when I press it again one folds out/the other folds in, and so it continues!! It has now happened for the fifth time & the dealer (Stratstone) is saying they will charge to rectify this as the warranty has expired- can that be right when there is an underlying problem they have failed to solve previously??