Pull it out completely, and clear it out. I had the same problem on my E36,
found that the jack point had become clogged with silt which was stopping
the water draining out - the sunroof drainage runs into the sills. Since
cleaning it out I've not had any water build up.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.