So my HTC One had the issue with where in low light I get the purple tint. I called AT&T and they said they will send me a new replacement phone and I just have to mail them back the old one. So the one I have has a custom ROM on it and the bootloader is unlock. Before I send it back, what should I exactly do? I'm assuming I should put a stock ROM on it, guessing there is one out there. Do I have to relock the bootloader? Thank you any advice would be great.