I've had mine for a few months and I've detached/attached the neck of it many times, and have yet to have a problem. You're friends obviously treat their stuff like crap.
The other friend got it less than a week ago. His was crap straight out of the box. Maybe its just a certain batch of them. Or PAL ones in general :P.
Point is they suck and the affected ones need to be taken back and replaced as new.
I only found out there was a problem after getting pissed off that I got beaten by a 15y/o girl >.>.
When I'm proud of doing Raining Blood on Expert, that kinda hurts XD.