did you try different brands of ammo?
Does this occur each time a cylinder "full" is loaded and shot?
Did you "look" to see if you have bent crane? The smaller revolvers are often abused by ignorant shooters who "flip" the cylinder closed. I bought a used Colt Detective that had a bent crane and missed it when I examined the gun. I sent the revolver to the factory to be repaired and it is good as new.

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JIM
NRA Pistol Instr