and yet anotherThat's quite a silly thing to say. Just because you never had issues with it does not mean the gun is perfect in every way, or that every problem can be chalked up to user error.
GK1's are not identical clones. Each one comes out of the factory a little different. I have one of the earliest models, and mine happens to have a slightly oversized magazine, and therefore is a little more picky about ammo. It happens.