With the side lock,I had a repair problem with one and it took me several days to recognise the problem. I thought cocking,springs,etc.,but with this Beretta it was the little pins that lock the cocking rods.If not locked, the inertia of the rods impedes the strike of the hammer and the gun does not fire much of the time.I made new locking pins and problem solved.Perhaps this is your gun's to be problem.