The
controller went bad on my HD last March, and Kobo got a replacement unit to me, which has had no problems. My lines were white, and my screen was still responsive, but I thought I'd link you to my experience in case it helped.
I went to Chat for help, and had a txt file outlining my issue that I posted after each rep asked how they could help. Didn't want to waste anyone's time covering the same prefab questions over and over. I also followed up via email. My return was not without snafus, but once I got the right CS rep my situation got handled properly.
I made sure to be persistent, polite and factual with CS, and after a few tries I got my problem solved.