So ...

The drawbar head doesn't jump when the trigger is pulled (slide off to enable seeing it) in SA mode?

The drawbar plunger and spring are in good condition?

The drawbar isn't cracked?

The trigger pin freely rotates when the trigger is pulled and released?

Okay, IF this crunchy-whatever is happening when the slide/barrel are installed and the gun is fully assembled ... and it happens during the trigger pull ...

I'd still check the drawbar, particularly on the R/R corner, where the firing pin safety exerts pressure against the front of the drawbar tail as the lever is being pushed upward ... and ...

I'd inspect the freedom of movement of the firing pin safety plunger (steel plunger, on right side of slide). If the firing pin safety plunger spring has been clipped, bent, folded over or otherwise damaged when the rear sight base was installed (originally or later on), the plunger may not be moving like designed.

Video clips are often much less helpful than you might think. They don't let you handle and FEEL what's happening, nor do they usually offer the angle or perspective that's desired. Obviously, they're not a substitute for being able to handle, disassemble and inspect anything.

Sometimes, as was already mentioned by someone else, I thought, little weird "problems" can be the result of unrecognized assembly abnormalities. You'd be amazed at how easily a sear tail can be located on the wrong side of the sear spring, for example.

Sounds like this pistol ought to be carefully checked out by an armorer or gunsmith familiar with S&W TDA pistols.

If you lived near me I'd be happy to inspect it as a courtesy. Sorry.

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Ret LE Firearms inst & armorer