I have a 2011 e550 and the drivers side seat has reclined to a position that makes it very uncomfortable to drive. The power seat controls have no effect on raising the back support .it will only allow me to lower the back support.   If i try to raise the back support it doesn't fully go all the way up

 

 in the attached image you can see how the drivers seat is reclined compared to the passenger seat.

 

Any idea on what may have happened and how to fix it?  My back is killing me when driving.