It has been my experience with VW crank-back sunroofs is that those clever
German's designed them to leak.  Instead of preventing water from entering,
they merely told it where to go.  Every "leaker" that I have fixed only
needed to have the drains cleared.  Many folks were not even aware that the
drains existed and spent/wasted a whole bunch of time trying to stop the
leaks.  Most ended up by disabling the sunroof ala duct tape.
Check those drain tubes first.  Unless the felt seals (more for drafts than
water) are completely shot, the drains should be able to handle and water
"leaks".
Good luck,
Mike Pidcoe