i've had an issue with pullups that might be relevant. in the school gym, they have several OL platforms w/ racks w/ pullup bars on them. some of the pullup bar grips are so rough and gritty that it kills my hands to do much on them. others are pretty smooth and cozy and i don't feel any pain.
i've noticed that my reps and strength output seem to be better on the smoother ones. i think it's because i tend let my grip slacken more on the rough one since it hurts to squeeze too hard while repping something out. this open grip might tire out quicker which causes everything else to work hard to compensate.
dunno if that's exactly what's going on w/ my numbers on those pullup bars or your kb issue, but it's a possibility.