If you roof seems to get stuck about 25cm from close, you may have a problem with the way the roof canvas folds.

It is common for the last fold to end up pointing down inside the car when the roof is initially lowered. With the roof stuck, you'll probably find that it is jamming under the roof bar seal (circled below).

A temporary fix is to lower the roof about 5cm and from inside the car, push the fold outwards. The roof should close normally.

A more long term solution is to 're-teach' the roof so that it folds normally. With the roof closed, soak the canvas in warm (not hot!) water and wipe off of the excess. Now lower the roof whilst keeping an eye on the problematic fold. As soon as you see it start to fold inwards, push it out and continue to the lower the roof. With the canvas gathered up in the boot, crease the lower fold quite hard along the whole length of the fold.

Pay particular attention to the straps which are located approximately as shown. Give them a thorough fold.

Allow the canvas to dry in this position (i.e. keep the roof down for a while). Then try raising the roof and the problem should be cured. If not, repeat and clamp the straps with a large bullbog clip (or similar). This may leave an exaggerated crease when you raise the roof but this should soon flatten out.