I've got a Crossman pump master ive had for probably 15 or so years. I went to shoot it the other day and it pumps up but then when you shoot it has no power first shot but if you load it without pumping it will shoot 3 or 4 times at a low power like the air is getting trapped somehow. Anybody have a clue as to why it would do that? Ive had them blow seals and thats easy to determine but uve never seen one do this before.