My E-class estate is letting in water and I know not how! After heavy rain, or if I use the jet washer, the next time I open the tailgate (see pic), water leaks out from the inside of the tailgate where indicated by the arrow (see pic). Sometimes water leaks from the right side and sometimes from the left. Does anyone have any idea how/where water is getting in and what the fix is please? The rear lights look fine from the outside (i.e. no condensation visible). I'm wondering whether water is getting in via the gap at the bottom of the rear window? Many thanks as ever.