The two orings on the end of the regulator pin assembly seal the front chamber from the air inlet while allowing the pin assembly to move back and forth in the valve. The reason there is two, is so that the unregulated inlet air can't bypass the first oring and get into the front chamber. It escapes out the side port instead. If a piece of dirt gets in or on one of the two orings, it can prevent the oring from sealing the air. The orings are separated by a plastic split ring. Try cleaning the orings and the passage they sit in first. Then if the orings need replacing, follow the link in the post above and you can easily replace them.
Except for the Automag in front, its usually the man behind the equipment that counts.