While I am pretty good at bare shaft tuning, and normally am able to get the tune I want, there have been times I have been unable to get rid of a persistent nock high. One option is just don't worry about it. As long as you're sure that the nock high is a true nock high and not a result of deflection of the shaft off the rest, it really doesn't hurt anything. The last time I had that condition, I tried everything until I was pulling my hair out, and finally happened to try a bare shaft of a different brand, and the nock high went away. I really have no idea why that worked.