Our driveway is at an incline so I also noticed the same thing as you when the electric brake is engaged during parking. I also noticed same thing on my wife's Odyssey minivan parking foot brake. On that it moved a bit more than the GLC. It was a bit unnerving when we first bought the minivan, but we got used to it. My Civic Si has a handbrake and like you said, car doesn't move once it's fully up. I'm still trying to get used having electric brake. There's something to be said hearing that clicking noise when engaging manual brake that gives a sense of security knowing that the brake is engaged when parked. Just like everything else, I'm sure I will get used to it soon enough.Going back awhile I liked the good old fashioned handbrake, pulling it up knowing it was fully on, then I had a B-series which was my first introduction of a electric handbrake, being unsure for awhile, but being quick won over when applying it on our steep drive and not moving an inch once applied and then the auto release function when moving off. However with the GLC I have noticed that once the handbrake is applied it moves ever so slightly. Has anyone else experienced this?