I tried again this afternoon... no success. Stopping with the parking brake @city speeds is impossible. Other scenario: I pull the p brake as hulk and 2 times out of 3 the car moves forward in D without any throttle...

Burnish the brake shoes would be a option to try... but I‘m so sick of trying solutions that I will just stick with another set of new shoes and see if it gets better.

Thinking of it, it cant be that the parking brake efficiency of the e53 is like standard like mine. What if the car would be a manual transmission = no parking pawl. You couldn‘t park the car on the slightest slope...