Well I read mostly good things about the JG AUG, I guess I just had bad luck.
I'm probably going for the PicoSSR FET.
Now I just have to figure out how to wire it.

Just send it to a local gun doc with experience on MOSFET...

Local isn't the correct word in my country :/
The closest shop that MIGHT repair my gun is like 1 hour driving.
My friend and his dad would like to help me, perhaps they can figure it out.

it's pretty easy, there's diagrams all over google on how to wire a MOSFET.
I'd suggest upgrading your wiring to something higher grade though, RC hobby shops will have wire.

Where have you heard this?

Okay, here I am again!

I got my new fet today (PicoSSR) and installed it in the gun. The gun shoots again, but the bb's often double feed or just fly like 15 feet.
Does anybody know how to fix this?
EDIT: oh yeah, when I shake the gun it sounds like there are quite a lot of BB's in the hand guard.

Found the problem.
The gearbox was loose. I put pressure on it with my finger and the gun worked perfectly.
SOLVED

That's normal on AUGs and P90s. The soldering tab is actually a U-channel. These soldering joints look a lot better than on the JGs I worked on.