Rifleman, yes, feather placement can make a substantial difference. However, one can usually get proper clearance by adjusting the brace height and nock point.
I suspect your brace height might be a little low causing the arrow to bounce off the side plate and give you a false stiff reading. It's likely that only the feathers are hitting the side plate, but they're hitting hard enough to throw the arrow off. Turning cock feather in reduces this possibility. So does raising the brace height. Good luck.