I've seen a lot of QFR problems, but I have yet to see one caused by a bad controller. It's usually the soldering work or PCB that's the issue.
PointyFox: Do any keys register or none? Do the lights turn on and off corresponding to the caps/scroll lock modes, or do they just blink once when you plug it in?
Defying: A series of adjacent keys not registering is most likely caused by a trace on the PCB being shorted or intermittent. In some cases, loosening up the screw on the back of the QFR will solve the problem. If that doesn't work, you'll have to open it up and inspect the trace connecting those keys more carefully for any breaks.