I was gifted a 9mm 469 pistol. The gun goes from double to single action on its own, meaning, first round is DA, second is SA, next two DA, back to SA, back to DA...
I think it may have a fairly high round count. Any idea where to start in the trigger group? Thanks in advance.

Welcome to the forum

First, I would try a complete disassembly, cleaning, inspection and lubrication of the gun. There are so many issues, including dirt and old lubricants, that can cause the problem you reference here, that a shot at an actual diagnosis would be futile, pure speculation, and might even lead you in the wrong direction.

If you are unfamiliar with the disassembly procedure and what to look for, you can check with some of the local PD's to see if there is a S&W trained pistol armorer in your area, or a qualified/trusted gunsmith who is familiar with these models, who could have a look, and try to determine the problem.

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Ret. LE, FA Instr, S&W Armorer

Depending on the serial number, you may want to contact S&W to see if that pistol has been serviced under recall. That would be one way to have the pistol serviced for free by S&W.

See text of recall here - Smith and wesson 669

Probably best to have it examined by a smith or S&W trained armorer familiar with S&W TDA pistols.

The inability of the gun to remain in SA mode after a shot is fired (and another round has been fed/chambered) can be the result of being either very dirty, or any of up to 4 different parts (or a combination of them) being damaged/worn.

If a proper detailed cleaning doesn't resolve it, then it needs to be evaluated and diagnosed by someone familiar with the guns.

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Ret LE Firearms inst & armorer