Convertible roof opening incorrectly
 

My Mini Cooper convertible (2014) has a toggle near the rear View mirror to open the roof with. Usually when you pull the toggle forward continuously, the sunroof retracts fully, then you have to pull the toggle again for the full roof to retract.

When all windows and roof are closed and I pull the toggle forward to open the sunroof, but it only opens 10cm or so. I then have to pull it forward towards me again, so it opens a further 10cm and repeat again and again until it is fully open.

Has anyone else seen this on their car and if so how did they fix it?