I don't know if what I am about to describe is a problem with arrow flight?
If you take a longbow and hold it at eye level looking from belly to back the shelf on most bows is somewhat flat on the surface from inside to outside . Some are slightly radiased.
What would happen, if looking the same way,the shelf was dished or U shaped. the shaft sitting in the U about 1/3 of it's diameter.
Would this cause erratic arrow flight.Would it cause arrows to fly weak by forcing the arrow to flex incorrectly upon release?
I have such a bow. It can be canted almost 25 degrees before the arrow will fall off the shelf.
It's a good shooter but all shafts strike target weak no matter what the spine( within reason) even being shot with a release aid as to avoid any plucking.
There's one way to find out if that's causing a problem LS. Take a sticky felt pad and place it on your shelf, re-adjust string nock and let 'er fly. Some of my bows are like that and I've not noticed any problems..........Art
Just build it up with moleskin to flat or slightly peaked and see if it cures your problem..
put some lip stick on your fetching and see if you are getting too much contact with the shelf. the above mentioned will cure the problem by building up the shelf... i use velcro pads myself.