Weird that this is the case with the OEM mag but seriously it could be that their moulds are just slightly off and none actually seat properly. Take for example some airplane that had it's left and right sides designed by two different teams in 2 different softwares (I think it was something like Microstation and Solidedge in this case or whatever), the fact is when they went in to put the plane together, nothing lined up.
It could be that the mag and the magwell/body design were done by two different teams and their tolerances didn't line up correctly.
I've had to do weird things with various mags, sometimes even cutting away at the mag catch area to get it to seat properly or putting a couple pieces of tape to shim it ever so slightly to get the holes lined up or even cutting away at the BB stopper inside the mag with a circular file to try and get the BB's to centre themselves in the channel when coming out.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE