Not to worry IMO
...
Any gun, NIB, then to the range for the first time, goes thru some kind of break-in period. Some go 100% right out of the gate, others cough, now and then.
My bet is simply that she needs a complete cleaning, as they pack them with thick, long lasting, lubrication for protection from rust, as to ensure that in the time she leaves, to the time she is bought, no rust, corrosion, can occur.
It sounds like a case of "timing" that is not so much about 115gr vs 147gr, but rather a magazine issue, as it doesn't take much for some grit, to cause the timing to be off at a certain load-count, with that mag, or mags..
Clean both, the gun, rails, feed ramp, breach block, everything and put some fresh oil on her, along with, and most important, open up your mags, and clean them out, along with the springs, everything, and then use some kind of dry lubricate for the interior walls of the mags, and the springs.
EEZOX (a synthetic lube/*light-cleaner, in one) is great for your entire gun, but especially for the mags interior and spring, as it cleans, and then once wiped, you then put on a very very light coating of it on the interior walls and spring, let them sit for some 5 mins, as this stuff bonds to metal (it's all on the directions) and makes metal to metal contact slippery without attracting dust, dirt, and more important, powder residue..
It will not harm plastic and makes any of the plastic parts glide over metal far better, as well.
Keep us posted..
Ls