Cgs synth

Hey all, I've just built 4 of the serge resonant eq's. 2 of them work perfectly but the other two each have two bands next to each other (different for each board) that don't do any cut or boost until the very end of the pot travel at which point they short out the signal. I have looked for solder bridges and cold joints and haven't found anything. All 4 were wired the exact same way. I swapped chips out on one of them and the problem didn't move. Before I start reworking the boards on those bands and risk lifting traces etc I was wondering if anyone had run across the same problem at some point and could point me in a productive direction? Thanks!