not to debate, BUT if he changed his form to a different way and repeated it, the same POA would be the same shot after shot

how he grips the bow, release or anchor spot
if it was once here and now there, but he repeats it
the shift will be the same OFF , due to form

I am sure a rest can move and also be the issue
here
but if he said all things were tight?
I doubt they moved and then got tight again?

Form is a HUGE part of archery/bow shooting

just like guys that shoot from a treestand and then don't bend at the hip and miss?
Form /was bad and odds are the rest was all right?

that's the main reason they practice and more practice is what makes you better shooter, you develop muscle memory to stay in FORM

I'm not perfect by any means, but its still my guess here!