just booked an appointment with my local bmw dealer. The problem is very well known to them. Changing the rubber seals is not a long term solution - the creaking sounds will come back eventually.
BMW has developed their own solution. its some sort of lube they apply on the rubber and it does work. The stuff is expensive tho, good thing i still have warrenty...
You can only buy this from your BMW dealer, it is OEM.