I can't tell you what the problem is, but I can let you know how to design a hunting arrow so it has a good chance of going where you're pointing it.

Lots of weight on the front will resist outside forces that tend to make the arrow plane. 85 grains is very light. The heavier you go, the easier it is to control the arrow.

Arrow spine has to match your tip weight combined with draw weight, arrow length and draw length. This can be a difficult concept for some, and you're already limited. You already have an arrow at a set length. Most trim there arrows to shoot as short a length as possible, leaving no room to trim them. Your draw length is fixed, so hopefully you can adjust the draw weight on your bow.

The third component of a good hunting arrow is one with a lot of drag on the rear. The fletching should be light weight, get the arrow spinning (helical or offset), and offer lots of air resistance. Feathers are great at all of these.

From your description, I'd be willing to bet that your arrow is under spined. Combine that with a light broadhead, and well, have fun hitting anything. I'd recommend starting over and getting as much help as you need to get the next set of arrows designed for hunting with your setup. I'm sure that many here would be willing to help. To really evaluate your current setup, we'd need a whole lot more detail on both the arrows and the bow.