I've had this, and had it 'fixed' at a main stealer but that hasn't cured it for all time
It's something to do with the mechanism going out of alignment.
On mine, I've to get out of the car at various points and man-handle the roof to get it to open and close properly.
I found the lever on the passenger side (within the hood) wasn't quite locking-out at the end of the cycle.
A firm push on this locks it out and the roof can then be properly sealed via the button in the normal manner.
I wouldn't bother paying someone to 'fix' it unless you need it 100% right to sell it, just set an hour or so aside and have a good 'do' with it.
I've spent well over £500 on mine, and that was for people just to 'mess' with it.
It's never needed any new parts, just re-alignment, re-calibration, whatever you want to call it