I have the mysterious leak too. The dealer did a water test and says there is no leak. However, both times it has rained (only had car 9 days) the fabric above the plastic on the post between the windshield and the door gets soaked inside. No water anywhere else.
Yesterday I took a garden hose and flooded the roof around the roof rack and the windshield and no water got it. Waiting for next rain to see what happens.
I do NOT have sun roof.