The smallest of scratchs will cause a leak. If its on the valve then will more than likely just need a replacment valve. Have you checked the rammer housing face? Best to get a really bright light (we use halogen lamps)and check the face again the smallest of scratchs will cause a leak. Also have you tried dry firing the marker for about 30 shots with the new valve in this can sometimes stop leaks as the valve can sometime need bedding in.
yeah, its the housing face that has the worlds smallest scratch. tried the replacment valve and many shots through it... like i said, planet are getting a phone call tomorrow morning, see if they cant fix it.