Just wondering if anybody else has a problem with the alko aks 3400 hitch being very hard to push down, all my vans that have had this hitch have been fine but my fathers hitch is so stiff you have to stand on it to engage it. we have tried stripping it down and cleaning all the parts including the friction pads and have now replaced the friction pads but still it refuses to engage without great force. we have also tried changing the tow ball but still no result, totally baffled as its not really that technical a product but its defeated me this time, any ideas other than throw it away ?.