2004 BMW Z4 roof motor

The roof has stopped working, when you press the button it pops up an inch and then stops it will come back down when you press the close button and lock but will only come up an inch when you press the open button. On the odd time it will work an d open. I have been told it needs a new motor and bmw want 1600 pounds to do the work but I have not taken it in for them to check out. Do you think it will be the motor. I have also been told that there was a lot of the z4 of this year that have the same thing