anything that is not perfect will cause the wobble. the faster you turn, the more the wobble shows. Crooked shafts, not a perfectly symetrical chuck, too long of a tube (if tubing is used) causing a bounce effect, not straight arrow.
One thing that could maybe fix all of that is for one of us to put together a means of rollers so that the arrow is not merely suspended and touching one or two supports, but is actually held in place, top and bottom, in a couple locations, such as near the nock and just past the area where you will crest. That should at least keep that portion from vibrating very much, unless of course the arrow is REALLY warped in that location.
Oh, if you do this. . .please post pix and share
ChuckC