To me,

Sounds like a botched windshield installation. There are several little folds of rubber in the seal. I bet if the windshield was pulled out, you'd fine the inner part is pulled under. If this is truely the case, it would take a huge amount of goo between the body/rubber to seal the offending leak.

99% leaks on the floor boards are orginal leaking front window seals, but everyone looks at the sunroof.

You can try pressure washing around the seal to simulate the storm.

Did they put a new seal in ? Was it an MB seal? Was the tech familiar with Benzs?

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E