problem with redwolfairsoft upgrades

[vekcna]

hello
so far guys in my team purchased 4 upgraded AEG from redwolf. Two with 2 level upgrade which are fine (TM MP5 and TM G36C) but the other 2, didnt work well from day one. the problematic AEGs were "TM M4 new ver" and "TM AUG" both upgraded to "level 3" which upgrade the gun to ~400 fps and inclued the following:
1. Install Prometheus spring ( Prometheus Non-Linear Spring MS135 )
2. Systema Bearing middle gear
3. Systema Steel bushings
4. Systema Steel gears
5. Battery Compartment Mods
6. Fuse removal

now for the problem... the two guns can shoot with the 9.6v 1700mha about 400 rounds and in this stage the battery is on the verge of boiling. we dont know what to do, we tried to lower the engine under the assumption that its squeezed to the gears but that wasnt the problem and now we are clueless.
we would appreciate any tip you guys can share with us
thanks
Vek