When I first switched over to the new style biscuit I was getting slightly wavey vanes and switched to a better quality vane.That cured the problem, I then realized I had the wrong size opening biscuit. I got the correct size for my arrows and never needed to put on expensive vanes again.
I think hole-size on the biscuit is one of the things most people don't pay enough attention to. To get a "forgiving" biscuit as well as one that doesn't damage the fletching, I think the fit should be rather sloppy. I've experimented shooting the WB with a really large hole (probably twice the diameter of the arrow) and the arrows flew perfectly. I've seen more problems when the bristles were real close to the arrow. Even if it wasn't a tight fit, small problems would occur on some setups.