Usually, the inability to achieve level bare shaft flight at any nock height is due to a form issue. However, you state that your other bows bare shaft almost perfectly, so I assume form is not the main culprit here. I assume you don't have a problem with nock right or left, or you would have mentioned it, and the spine you selected for your arrow seems appropriate. Possibly cutting your shaft back to 29", which would require you to use a somewhat heavier point, might improve arrow flight. Possibly changing your brace height might help. It could be a tillering issue with the bow itself, which you can't easily do anything about.