Rubbing passenger window

Has anyone with a R129 had problems with their passenger window rubbing against the hardtop/softop frame when going over bumps or dips? My MB dealer is servicing my car right now and has completely taken apart my door to identify the source of the window rubbing. Originally, I was told by my service advisor that the rubbing was just normal body flexing that all R129s suffered from. Not being satisfied with that answer, I eventually spoke with a senior service tech, who, after going for a ride in my car, agreed that the window rubbing wasn't being caused by body flex -- he thought it was something in the door that was loose. Since my ride along, the service tech lubricated all of the window rails and guides inside the door and has proposed to replace the felt-rubber seal/guide that is on the leading edge of the door, pressed against the window (supposedly keeps pressure on the window whenever it's raised). He can't find any loose parts. Will changing the felt/rubber seal make a difference? I've authorized the dealer to replace the same, at a cost of $300 -- just hope that I'm not chasing a false solution.