QA Consultant here. I can't stop laughing, and I'm dearly sorry for what I do - but the only thing that makes me weep is because I'm under like, 3 layers of leadership between me and the client, I can't even tell you directly, clearly what's wrong - I have to use software and methods that are often imprecise to tell you, and I can't take the liberty of adding a note on how to fix it because "it belittles you". But seriously though - most common errors made is because you look too hard to get the answer and stop caring how you get there. (And those who aren't is because you're dead tired after many restless nights because of me :D) PS: if I may give a tip, when you plan on having several very similar elements, don't instantiate. Build yourself the tools so that the original serves as a template and the rest is modifications on top of the template. Because otherwise you get inconsistencies and can even break everything else.
I refuse to repost this as it's pretty much everywhere...but check it out if you haven't yet http://www.gamasutra.com/view/news/249475/More_dirty_coding_tricks_from_game_developers.php
Oh man, I think I know what bug they're talking about with the PS3 UE3 code. I worked on a project that had a similar issue, and I suspect they used a similar fix. At any rate - good stuff.