"Every now and then one might shoot pretty good, but then all crazy again. "
Did you number your arrows? Swirling to the target....like missing a vane? So you have 3 things in my mind....1.your arrow is hitting something coming off your bow...rest, cable, sight, etc... .2. you are gripping your bow hand...torqueing the bow, should be in the soft spot of your hand, grip open. 3.Your draw hand is torqueing your release, assuming you are shooting a wrist caliper, you have more than just your trigger finger on the release, maybe a 2nd or 3rd finger gripping on the strap coming up through your hand...
Hope these ideas help...