Re: Broadhead problem.
Probably the arrow. The air that broadheads catch will multiply and problems with bow tuning or the arrow. With crossbows, tuning is not as much of a issue. I suspect that your arrows are the culprit. Either not enough spine for your fast bow or not enough weight forward.
Since it seems the fixed blade is flying the best, also make sure your mechanicals are properly closed and not prematurely opening.
I support all hunters, regardless of weapon or technique!