Nock high can be a multitude of things. Most have been mentioned. I see carbons do it more than any other arrow type, without even a little exception. It could be inherent in your form, form vs arrow recovery, arrow spine/weight combo, nock height, messy bow build, nock tightness, brace height, finger pressure, release and even bow weight to release. Some people have a hard time with low bow weight not ripping the string from the hand. My main fix is first get rid of carbons. It’s so easy to tune aluminum or wood. Then, once you are convinced you can shoot a straight arrow, go back to getting crazy messing with carbons. I gave up shooting carbons except out of my one recurve. I’ve seen many fix it with moving away from carbons. That said, some folks have zero issue. I think carbons just recover so fast, many don’t have a good enough, or quiet enough form to use them. So when your shooting sucks, move to aluminum or wood. Generally speaking a touch of nock high probably isn’t poor at all. Like someone said fletch em and go hunting.
I’m in the camp that tune with broadheads, and work backwards. Nothing will exaggerate poor arrow flight like throwing a broadhead on the end.