I would check the valve seals. On my legend the valve o rings were being shredded by small pieces of metal that were being pushed into the internals by the screws that holds the frame on as well as a set screw I believe. There is the o ring on the ram tip as well that could lead to cause that type of a leak. But sounds more like a valve leak to me.
You take the frame off and there are two screws by the front. One for the front block. Remove that the spring and poppet come out. If you look inside there a silver metal piece, valve body, which the poppet seats. The other screw holds that in. Take the screw out and pull the valve out. You may news to push with something through the while body like a long Allen key. It has two orings on it that if either fail will cause air to leak into the barrel or out around the back of the bolt ram area. Just make sure you put it back into the body in the right direction. And while it's out can do a cleaning and also check the screw holes for burs on te inside.