No need to disassemble the cylinder yet. Simple spray some air into the front cylinder lock, and make sure it’s functioning smoothly. That looks like a trap even a couple of rounds could jam up.
I bought a S&W Model 36 brand new about ten years ago. The trigger was binding occasionally right off the bat, so the shop owner and I took the sideplate off, and shook out 3-4 small steel shavings. Problem solved.