If you think a Mercedes is bad, try a Volvo 700 series. I've never seen such brittle plastic. On my W124, the only brittleness issue I've had was with the 3rd brake light. After trying a couple used units off ebay and finding they all had the same issue, I just attached the cover with a very light bead of silicone caulk. It holds the cover in place and can still be pulled off to change the bulb.