If you fire too many rounds down a real gun in quick succession at best you will destroy the barrel at worst they will be picking bits of receiver out of you. So again is that design flaw or user error? I would agree if a AEG locks up after a double tap that is a design issue, But the term "spam the trigger" was used and that doesn't bring to mind double tap. If you use a gun that was not designed to be a speed soft gun like a speed soft gun and it fails that's user error. We are obviously coming at this for to different mentalities of playing so we are not going to see eye to eye.
to the OP Tokyo Marui are still the best in the game for recoil that isn't going to cost 1.5k +. I have used a bone stock NRGS 416 with a 20c 7.4v 1300mha lipo for over two years and the gun has never locked up on me. Obviously other people have had different experiences all i can say is don't spend money on parts you don't need to.