I'll have to respectfully disagree on that. I had the Grayling and while it is inexpensive, there was play in the nock indexer(?). The result was less than perfect spacing between the feathers. I gave it away to someone ont his board.
Thats very possible , I haven't experienced it but it sounds feasible. Did you tighten the screw with lock-tite? I put 3 marks on my Bohning to make sure it's rotating to the exact spot every time. The quality of my Bitz is definately better (steel -vs- plastic) but the end result is the same.
Just trying to point out that you dont have to spend a fortune to get started in doing your own fletching.