I had an issue with my light set up a few years ago. I was shooting rage broadheads, hit the front shoulder and got little penetration. He survived. I was devastated.
I was so scared to hit closer to the shoulder that I unintentionally found myself hitting deer too far back and getting liver hits.
I wound up going very heavy (70 pounds and about a 620 grain arrow - 100 grain stainless insert and a 150 grain fixed blade broadhead).
I spent a lot of time tuning the bow myself and have it shooting perfectly. The result is great confidence and aiming closer to the shoulder, knowing if it's not a perfect hit and the shoulder is involved, the arrow will still do it's job.
I see a lot of people against heavy arrows and passionately defending mechanical broadheads saying things like "I have shot dozens of deer with a mechanical and have never had an issue, all pass throughs and all of them died quickly" which is always our goal as hunters.
If I knew every shot I took would 100% of the time hit just behind the shoulder and perfectly pass between two ribs as it blew through both lungs, then I would probably shoot light arrows with mechanical broadheads. Plan A is to hit where you are aiming but we all know things happen. A small deflection, a deer drops at the sound of the shot, nerves. My decision was to be sure if plan B was needed, my arrow would still do the job and blow through the shoulder instead of just sticking in it.
I shoot my finely tuned bow now with great confidence.