Shoot bare shafts through paper at like 10ft then 30ft. If true, fletch and broadheads should be almost done flight wise. Fine tune and run it. Fixed blades require you to put some effort in to perfect flight in most cases.
my bare shaft is rarely perfect once I am broadhead tuned. I have found papertuning is good for initial set up but getting a BH and FP to hit the same at 30 yards usually leads to down range accuracy. small movements with the rest of 1/64 or 1/32 go a long way
For sure, broadheads can be strange. I go as far to number arrows and broadheads that fly true and that arrow never changes after that. For whatever reasons I have had times where one head would be a dart then another of the same head on the same arrow is off a tad. They aren't rifles lol
