I' ve never seen sheild cut and parabolics change things that bad. Something else is going on here.

You say these arrows are significantly heavier than your last set of arrows. That wouldn' t cause them to paradox any differently, but that significant weight might just might be a tipoff that their spine is different from your last set. Different spine would definitely paradox different. I' m not much of a believer in paper tuning stickbows, but I would bareshaft a couple of these arrows and see how they act.

The bit about the black stripes on the arrows from the strike plate is screaming bad spine, at least to me.

I don' t understand why you lowered your nock point... lowering your nock point will cause MORE contact with your fletching, not less. I would raise the nock point and also raise brace height and see what happens. If it gets better fine. If not, lower the brace height. If neither works, then try heavier and lighter tips. If nothing works, you' ve just got arrows your bow doesn' t like.