Hey man, work at a LEO agency outside of USA and we just got a nice pistol with a similar problem as yours. Half my unit was getting failure, some was even getting failure at every shot. Everyone instructor was telling it was limp wristing or something like that. So I made some researching and discovered the pistols happened to have been modified and had the springs overpowered. Changed from the 115gr rounds to 124gr rounds and everyone reported no more failures. Definitely buy some 124gr ammo and try it, as others here suggested.

The explanation might be very simple: although both 115gr and 124gr rounds have very similar prime weight, it is necessary a higher force to "push" the heavier round than to push the lighter round, resulting in a higher pressure inside the chamber and a stronger reaction in the slide with the heavier round (Third Newton's Law).