The motorized seat-belt presenters/extenders commonly fail when a plastic gear strips, and opinions split on how much it matters. One veteran dealer warns the parts are largely NLA and not worth chasing (a replacement motor quoted around $1,600, owners often just unplug it), while others say it is a cheap, non-deterring fix. …
Seat-belt presenters/extenders: NLA parts, disputed cost
Mercedes-Benz W124 E-Class · ownership