I too have had mixed results w/ Pro-Mag & Triple-K.
Pro-Mag: Ruger 15rd mag for P95/PC9...Junk, Hi-Power mag Good to go.
Triple-K: Hi-Power Mag...junk, Walther P5 Good to go.
It's hit & miss w/ those two companies...mostly miss it would seem from most people's experiences, I consider my self lucky to be at half 'n' half.
As a side note I have over 500 rds out of my Pro-Mag HiPower "range" mag w/ no mals, and 200+ rounds out of the Triple K P5 "range" mags w/ no malfunctions and no signs of breakage, feed lip cracks,deformation, weaking of springs, etc....
Will I buy from either again? no, probably not, too much of a gamble...