How do you fix the passenger side mirror to rotate down when put in reverse on 2003 BMW 325i?

I don't know about the 2003, but I recently bought a 2006. When the power mirror adjustment button is selected to make the driver's side mirror active - that is, to adjust that mirror - the passenger's side mirror will rotate down when you shift into reverse. If the adjustment button is selected to the passenger's side, the mirror will remain stationary when you shift into reverse.