I'm inclined to agree with TFOX. Having not shot for a while I'd bet it's a form issue, although you might not think so. You might find as you get more in-tune with the bow you have to move your sight back nearer it's original position. Heck, I see changes of a couple inches from day to day just from using cold muscles.

Years ago, when I shot a lot of field and target archery I would start out with the sight in one position and as I got farther through the course I'd have to change the windage a bit just because my muscles were working different. Guess that's why warming up and having an adjustable sight are all about.