KWA RM4 piston stripped twice in under 3k shots

[Katana]

Nothing has been changed internally except an m120 spring cut down to make fps a hair under 350 and externals have been changed

Only thing i think it could be which is what I'm asking about is the pts epg-c grip. I have read posts stating that the wires have to be routed a certain way otherwise the grip angle will be off and thus the motor misaligned. My question is, can this place excess stress on the piston to cause it to fail so quickly.

Furthermore the gun is being run on an 11.1v 25c lipo and seemed to die incredibly quickly the second i switched to full auto so to me it sounds like pme. Is this a possibility with only roughly 26-28 rps going through it if that. 

On this recoil system, is installing a swiss cheesed piston going to be a bad idea due to the extra stress on the piston in order to pull the recoil weight and spring. I just think a Swissed shs piston with AOE corrected may do the trick but no idea if it'll hold up under all that. The kwa piston has been ripped to pieces twice now though and I'm just looking for solutions. Yes, I have sent it back for repair with the same thing happen again in under 500 shots the time after and the guy is sending me a whole new gearbox but i want to make sure the same thing isnt going to happen here and also want to understand what is going wrong

Thanks

 

[Hangtight]

Grip alignment with have no effect on the piston.

Of you're  running a full stroke at 350 fps and 28 rps, then the spring will not be strong enough to avoid premature engagement. A cut down M120 is effectively the same as a M100. You might just get away with a M110 with a two tooth short stroke if you weren't running the recoil, but I don't know how much running the extra mass of the recoil lowers the PME ceiling. Someone with more knowledge of recoil systems might be able to chip in on that one.