XK8 Sticking roof
 

Hi, I have a January1997 Jaguar XK8 convertible,
When I pressthe button to put the roof down it works perfectly, but when I press the button to put the roof up again the door windows drop a little, as they should, but I then get a ding sound as though the operation is finished and the windows go back up.
If I give the roof a tug by hand then try the button again it works properly.
Is there something in need of adjustment?
Regards Karl