OK let me ask you, is it group size that is getting larger at 40 yrds over say 20-30 yrds?
and have you paper tested at 40 yrds to see if there still flying well, before you go and re fletch
many times group sizes open up farther out , just due to shooter error and not arrow issue's, or bow set up, but bow set up can cause issue's farther out of things are not set up corectly, just at closer ranges you don't notice them
I known a few guys that used to video there shooting , and then used slow motion to help see where the cause is
just something to think about before re fletching maybe!
I ;m no pro by the way, just my 2 cents