[mrerick]

Check to see how high the magazine has latched into the frame. If there is a lot of play it could be shifting down too low during cycling.

The issue could also be the magazine spring. Don't try to disassemble it yourself. People that work on these (Like G.T. on this board) have special tools.

Finally, consider that the recoil spring could be a 21 turn rather than a 17 turn spring. This could have too much power, and cause the cycle timing to be off.