[satz]

My guess too would have been the sunroof drains, but it looks like you've tested them well. I'm sure I've read other thread/s with exactly the same location of leak as you describe. They turned out to be the sunroof drain in those cases.

Perhaps the hole where the roof rail attaches to the roof might not be properly sealed?

Is yours the original windscreen?

PLease let us know how you go..