This happens every once in a while. It could be the rockers under the limb, but you did say it was torn down and greased. One thing comes to mind is the little washers at the limb tips that the cable yoke attaches to. These could be sticking a bit and not rotating smoothly as you draw.

It's not something common to Nova's. In fact, it isn't common to any bow. It's just one of those things that happens every once in a while. At least the shop is willing to replace the bow. That at least says he's willing to try to satisfy you. Give him credit due.