If your arrows corkscrew in flight to the target, then i would believe the issue is the arrow fletching.
Check your fletching, make sure they are in the the same position and one isn't turned/offset more than the others. Refletch the just one that is off.
Also try changing the position of your kokvein. Just give the nock a 1/3 of a turn to the next fetching and see it helps. If it still not flying straight then go to the next one. I always get one or two that i have to do this them, when i buy new arrows. So i get my flecthing all the same color and since i shoot a drop-away rest it doesn't matter to me.