I have similar issue with 12k hone. I don't know where it comes from. When i hone on 8k i get very good results and have good shaves. But when i try to polish the edge on 12k (after honing on 8k) it seems it dulls the edge (or does nothing to it at all). Maybe my techique needs more work but i've tried to finish the edge on this 12k for 2 months now without effect.