[DarkAngel]

1) its a mag not a clip.
2) the blowback assembly is completely independant from your magazine catch. The only possible issue could be that the mag catch is worn and the blowback action is causing it to "pop" off the mag catch assembly.
3) remove the valve, dab a little bit of silicone oil on the orings, replace and your done.

Mags leaking on gas guns are as common as fat kids on cake.

Edit : Crunch beat me to it.