I am guessing here, but it could be glazed or polished a little there. I am not really experienced with the Zulu but I am with other hard hones. When a really hard hone get super polished it get feeling kind of sticky because of surface tensions. The solution is to lap it so it isn't quite so polished. Lap it and give it a whirl. If it is still giving you a bad time then send Mike a picture and ask him his opinion.