Certainly don't want to second guess you, mobow, but if the deer is jumping and landing on the arrow (causing it to shift) why is the arrow not deeper (or a pass through) at 20 yards? Sounds like a penetration problem UNLESS the arrow is hitting the spine on the initial shot. My guess is the spine is stopping the penetraion which means you have another issue.

Right. I'm thinking maybe the arrow is only penetrating half way, then when the deer falls it pushes the arrow up into the spine...

Its not a tuning problem guys, actually itsa common, its no different than an arrow hitting a limb.
Sometimes the arrow goes stright through, sometimes it deflects off of a rib or other bone. I shot one onetime that was a perfect broadside and the entrance hole was right in the pocket behind the shoulder where it should be, yet the exit hole was almost at the end of the ribs on the other side and I have never hunted with a untuned bow or arrow.

Certain BH's do deflect more then others do!

I shot a deer last year from 33 yards and 20 feet up. Hit him perfect in the low 12 spot. The exit hole was out his spine. I was using a Axis 340 and a slick trick. Actually looked like I fliped the deer over. He ended up on his back with all 4 feet in the air. Didn't go but a few yards.

My last two years both my deer have been taken with internally deflected shots. Both deflected at entry off ribs. I was fortunate to recover both. I likewise use wasps but am thinking about switching to a slightly more rugged head with a better chisel point tip. (I am NOT blaming the BH for what happened, however they seem to have somewhat weaker, more bendableferrules than other heads).

I have a theory inspired by some here on HNI. I will be trying a slightly heavier arrow and insert to increase my FOC which is now around 10%. I am not sold on anything yet but we will see. Something is making my arrow deflect I believe. By process of elimination it can only be 1) the BH's blades and especially tip dulling or 2) low FOC and/or light arrow. I dont know of anything else that can cause deflections other than chance.

I know that these (Bullet Point) chisel point heads will deflect alot more. Just by looking at the design you can see that happening. I shoot Cut On Contact heads, thats one of the many reasons why I shoot them! To each there own though.