My gunsmith and I just stripped the gun apart, after I faced similar problems. He said basically I just shoot too much... But seriously, the disconnector can actually wear down strangely. Browning Buck Mark Parts: MGW #5. My gunsmith said do a full spring replacement, firing pin included...
Awesome gun. I put thousands of rounds through the gun used before I had any trouble. I'm confident with my gunsmith's solution. Try several kinds of ammo. Different guns can be picky. Mine will shoot golden bullet fine but not some federal... Weird... CCI tactical are excellent through it...