Because the round chambers when you use the slide release it sounds like you may be holding onto the slide, or riding it, forward when you rack it. I was taught to grasp the slide, push the pistol frame forward, then as the slide hits the back of the frame, let go of the slide. Alternatively, grasp the frame securely and firmly, pull the slide back until it stops, then let go of the slide.
Tap, Rack, Bang, my friend. Only other thing I can think of is you might have messed up feed lips on your mag, but most of these things are user error.
OK Found the problem - The slide stop spring wasn't positioned correctly
thus pushing the slide stop up all the time. Pushed the pin out and re-seated/re-positioned it. Now it's working fine.