Funny you should mention checkmate mags.. it is one of a very few brand of magazines I've had an issue with.
When I bought my 1st 9mm 1911, it was a Rock Island Armory GI model 1911
.At that time, it was the only 1911 they offered that was chambered in 9mm ( this was years ago) The issue I had was the mag wouldn't hold all the rds it was supposed to hold, w/o causing a FTF issue. Rather than contacting RIA (which I should have) I just loaded it with fewer rds. & it worked o.k.
Bought some Mec Gar 9mm rds, which worked perfectly. Eventually, I suppose the mag spring relaxed a bit, & it started working as it should.
Just remembered this , when I saw this thread.