I had a similar problem for quite a while, and the fact of the matter is, it could be any of the things mentioned so far. I am certainly no expert here, but from what you described, if your arrows are in fact correct spine, then it's probably your release.
In my case it was specifically my string hand. I was reading a post in the shooters forum one day, and a little light bulb went off. Terry Green was helping someone on a thread about string hand tension. He said something like "you're probably cupping your hand. Like this: ) ...instead of like this: ]
I went out, and really worked on keeping the back of my string hand relaxed and straight. Viola! Arrow flight problems straightened right up and shelf contact was a thing of the past. I was taking such a deep hook, and at the same time "cupping" my hand, that I was putting a lot of torque on the string, resulting in cruddy flight.
Not saying that's what you're doing, but you might check that. Good luck!
Curtis