Are you using a finger spacer. One time Mike caught me actually flexing the arrow down with so much finger pressure on the arrow.
I've seen that with some split finger shooters. You can actually stand back and watch them and see a huge deep bend in the arrow. And when released the arrow fairly leaps up into the air, rattling on everything even remotely close to it.
Anyway, when I was first learning this stuff I was SOOOO screwed up. You can be so out of whack that the results you see are near meaningless. Nock height issues so bad you would swear it was a spine issue. So far out on initial spine selection that the arrow is whacking the riser so hard that not only is it being thrown to one side, but up or down too.
Learned that not only can you get an arrow that is too stiff to whack the riser, but you can even get an arrow that is so badly weak it will whack the riser too.
Howzabout so bad off that the nock end of the arrow hits the riser so hard it cracks nocks? Not bad eh?
Nobody is born knowing this stuff.
Anyway, Stick, the advice to shoot vertical and sort out what is what is good. But what is the draw weight at YOUR draw length? Any idea? And what are you currently using for arrows, arrow length, and point weight? I know you said that it happens on ALL your bows, so it is probably something you're doing by accident when shooting. But what if you're accidentally making the same tuning error on all your bows?