On my 87 W124 230e I had loose rubber caused by incorrectly reinstalled plastic trim. Water ran under it, down the windscreen, missed the water run-off channel at the base of the windscreen and wet the fuse and relay boxes. Bad place for moisture, I'm sure it caused an occasional stall at low revs on very rainy days. I got silicone sealant. But first I removed the trim and rubber, cleaned dirt and gunk off windscreen and rubber with turpentine, slotted rubber on to plastic trim, then refitted, this time snapping the plastic trim firmly into the 3 retaining clips. Tight as a drum now, no need for any sealant.
John