I'm assumming you are decocking the gun when not in use or for storage. It is probbably related to the firing pin spring. Strip the bolt, clean out all the debris with a brush and good solvent, including the spring itself. Then lube with a synthetic oil, but lightly as not to create a build up. If there is any rust inside, remove it with steel wool. Also check the bolt release/cocking indicator on the side of the receiver and do the same thing. hope this helps.