J. Ko, I see where the confusion might lie. I am talking about raising one rear wheel with the jack, lets say to change a rear tire. In this position, with the E-brake on, and on a level ground, the car still has a tendency to perch precariously on the jack and WILL tip over if even a bit of pressure is exerted on the car. This is the situation I find myself in and I find one braked wheel on the ground is not sufficient to overcome the inertia of the whole MB tipping over (unless it is glued to the ground).
If your jack has given you none of these problems maybe I have a faulty jack, but I cant think of how. Suffice it to say I have little to no faith in this jack and will purchase a new aftermarket jack and wheel chocks.
Think about this, you say the jack is no problem on level ground, I disagree, but lets say your right. Well what happens that cold rainy night you blow a tire out and have to change it on an inclined road? I have never had a car move as dangerously as this with its factory jack, even on an inclined road. Be it Ford, Chevy, etc. I think that is one of the reasons this jacking system is not used anymore.
I love my Mercedes, but I think they messed up on this design in particular (along with the climate control and windshield wiper).