I have had similar problems and my advice is to continue shooting for some time until you can confirm a change. It could be a change in your personal setup (the way you look at your sights) that will pass or it could stick. I have never been able to prove that my bow setup has ever changed but I have had to change my sights after several practice sessions failed to bring my shots back to the bull. Not much help but it is my 2 cents worth.