Tony,
Any work or modifications by previous owner that you are aware of? Original grips? Magazines clean/replace mag springs? You might check the motion of the trigger bar....remove grip panel and confirm bar/assy moves freely up and down when magazine is inserted and removed, and that bar moves freely/fully (disconnects) up and down when the slide is pulled back, and released.

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Ret. LE, FA Instr, S&W Armorer