I have a model 36-9 (no-lock) that appears to have "Slow" timing. When the hammer is slowly pulled back in single action, there are 2 adjacent cylinders that do not rotate enough to lock up, even though the hammer is all the way back and locked.
This revolver sat in a bed side dresser and has not been shot that much and was never carried. Probably like this since new, but I never noticed.
On double action, it appears to be "just" in time (with just enough movement and none to spare), so the issue is single action only.
Is this something a local smith can repair with an oversized hand or does it need to go back to S&W.

PS: My newer 66-8 and 686 lock up noticeably faster.

Since it has been unused for a while, you could start with a thorough cleaning and lubrication. After the cleaning, check for carry up with two or three empty casings in the chambers. This will help keep the extractor lined up properly during the SA carry up check, and function check.

If it's under warranty and determined to be sufficiently out of time, I would send it back for repair.

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Ret. LE, FA Instr, S&W Armorer