Hi,
Reliability also depends on the type of pistol you stick the magazine in.
My 1906 Dutch doesn't really like the mec-gar and shoots/feeds great using a 1930s wood bottom blued magazine (crimped style).
My S/42 functions flawlessly with a mec-gar.
The postwar Mauser Parabellum feeds excellently with the mec-gar (better than with the original Dutch made magazines

).