Indexing mirror

[lesfinnie]

Hi my 2007 335d se l/h mirror should tilt when I select reverese, and it does but it is aiming at the road. I have tried adjusting it in the reverse gear position to allow me to see the rear wheel and then adjust it in the normal position for driving. That is fine but when I slide the button over to the right, as the manual states, the mirror works fine once then it has a mind of it's own untill you re-set it again. HELP!!!!!!