If you put your finger in the aperture and bend your finger towards the front of the car, you can feel a 'ledge' over which the locking pin has to travel. The top edge of that ledge is a beggar for rusting and a dose of fine file (not a yucking gret rasp!) will sort the problem.

It sounds as if some one has changed the lock and it has fallen apart and not been put back together properly had it with mine and it took me ages to get it right

Cheers for all the help everyone.

Had exactly the same issue with mine when I first used it, brand new L/R hitch and the car had never had one fitted before so the receiver was unused as well, changed the lock because I thought that was the problem, but in the end had to dress up the receiver slightly as it wasn't allowing the locking pin to fully engage in the receiver, now fit's a releases perfectly with no problems. Haven't used it a great deal but absolutely no sign of the "loose fit" issue that they have either.

Cheers
Col

Cheers for all the help on this people. Ended up getting it to fit using a file, loads of WD40 and some elbow grease to get rid of the built up grime and rust.

 Never argue with stupid people, they will drag you down to their level and then beat you with experience.