Here's alink from the PTW-users forum. It explains 1 of the problems from poor assembly practices:
http://www.systema-europe.com/Forum/...p?TID=1065&KW=
I'm not saying that anyone who assembles these guns is an idiot or anything, or that if there is a problem you were a twit for doing something wrong, but small procedural errors can lead to expensive problems. These are not a normal AEG here. They have extensive electronics for control and operation.
The factory builds them and tests them. Why mess with that?
And sometimes, parts will just break.