Identify your trailer swan neck
The tow hitch ball neck swan is manufactured by Oris, under the part number Oris 0107 2570/02, and carries the Mercedes-Benz part number A 163 315 03 99.
Trailer tow hook mechanism problem
Because few people know how to properly handle the mounting/unmounting and locking, it was forced and the fixing mechanism was out of the correct position.
It required a little disassembling and forcing back the star shaped handle in the correct position.
How to install tow hitch
In the video below, you can see the correct operation for the swan neck attaching/detaching on the OEM tow hitch installation (Code 550 TRAILER COUPLING).