The rear corner panels on either side of the tailgate (black plastic) can crack or break. They should be cut off and the adhesive removed before new panels are glued on.
Car Problem Reports
Mercedes-Benz ML430 Rear Corner Panels on Sides of Tailgate May Crack/Break
Mercedes-Benz ML430 Problem
Average Mileage: 104,666 mi (90,000 mi - 120,000 mi)