Leaks in the pneumatic system will cause problems with the dynamic seats and the trunk and/or door closing assist.Google+
Car Problem Reports
Mercedes-Benz SL550 Pneumatic System Leaks May Cause Problems With Seats, Trunk, and Doors
Mercedes-Benz SL550 Problem
Average Mileage: 28,825 mi (13,000 mi - 52,300 mi)
Visitor, 2008 Mercedes-Benz SL550, 13,000 mi
Trunk lid would not completely close and lock thus not allowing the top to retract.
The door locks worked intermittently.
$3400 for mercedes to repair!
Visitor, 2008 Mercedes-Benz SL550, 20,000 mi
trunk assist failed
Visitor, 2007 Mercedes-Benz SL550, 30,000 mi
pneumatic leak with battery drain