If you're nocking under the nock locator, 1/4" would be way too low, in most cases. A 5/16" arrow would be slanted uphill to the arrow rest, for example. I recommend that you start too high, maybe 3/4", and work your way down. If there doesn't seem to be any reduction in the nock high as you work your way down, then it could be that there is a tillering problem with the bow. If there is a reduction in the nock-high as you lower the nock point from 3/4", then set your nock point for wherever the nock-high stops diminishing. I assume it's not your release that's causing this problem, as you say you've tuned arrows successfully before.
If none of this works, and you just want to shoot the bow, then set the nock point at 5/8" and forget about it.