Type...
One point Id make is to check the Shield model.
You
may have bought a MA compliant version
or a older pistol with the trigger system that wasn't updated.
I saw a Youtube clip of a firearms/tactics trainer who also had a FFL. He requested a S&W Shield to T&E since so many of his tactics students had them.
He stated the Shield's trigger was awful and he disliked it. When he checked the records & the S&W factory box, he noticed he was sent a MA compliant version.
My no thumb safety format 9x19mm was made on 11/14/2014. It was
not MA compliant & to me, the trigger seems good. I'm not a M&P armorer or 3 gunner but the pull seems smooth enough.
FWIW: I handled a few NIB M&P full and compact pistols in the summer of 2014 that seemed to have rough, gritty triggers.
Hopefully Smith & Wesson corrected these M&P problems. I know they were grinding out 1000s of new firearms to meet LE contracts and sales.