My rear headrests shot up with a bump and will not go down I have the cabriolet and that is the rollover safety I assume. The switch on the dash would normally bring them down or adjust them but it is not working I hear the clicking and humming but they are not moving.

 

The rear headrests are usually controlled by that switch. But when they are shot up while going over a bump they have to be manually reset using a special tool. you should have it in your tool bag. It involves sticking the tool down by the headrest and releasing a latch, then your have to push them down. If you cant figure it out, most dealerships will help you out for free. Its common for them to shoot up while driving over a speed bump fast. There are angle sensors on the rear lower control arms. once a specific angle it reached (like a roll over) the headrest are shot up. Good luck