Do they all do it? Or just one or two. Number your arrows and pay attention. How do they group. If they actually spiral they will not group that well.

I would look at rest contact or something being seriously miss adjusted if they all do it. Normally for me it is a bad or bent arrow. A bad nock could probably do it as well, or messed up fletching. If an arrow is out of balance it will do it.

I have one arrow that spirals bad on the way to the target, I put it on an arrow spinner and it actually looks good? I have other arrows that are not as straight that don't do that. It must be messed up somewhere though.

It could very well be an optical illusion as well, or windy out. My arrows do crazy stuff in the wind. Try some bare shafting and see what happens. If you just reflecthed the arrows maybe the fletchings are not uniform and causing problems during flight?

Paul