I found with a mates aftermarket central locking the sheer shock from the central motors hitting the limiter on your lock after time moved the little brass thing with srews in it.( Dont know what you call it) being aftermarket they had too much throw for the vl door locks. Where the rod goes thru the little brass thing, i took the two screws out, bought two 4 fairly heavy springs and 4 collars (to fit onto shaft). Now on the front two doors only make sure you put them on the shaft in the follwing order. Collar spring brass thingy spring collar. Make sure your central locking motor is in the downmost position adjust the collars so the spring is just tensioned, do the same for the other way. (lock/unlock position) I know its a pain but my mate has now had over 3 years from an aftermarket set with no problems. Not bad for less than 5 dolars worth of bits! This will remedy the lock unlock situation alot of you get or bouncing hear it being called and also stop you wearing out you door lock mechanisms.