I decided last night that since elk season is upon us it would be a good idea to start shooting in my back-up string. I know I have great timing. Anyway, I put the new string on set the brace height and start shooting. Knowing there will be some string stretch I did not add a string nock, figured I’d wait awhile. I obviously have to just eyeball my arrow on the string and get what appears to be close and let em rip. I was shooting tighter groups then I’ve ever shot, although there was some erratic arrow flight, not every shot but maybe 1 for every 4 arrows. This goes on for a couple ends and really has me baffled, so I go in and tie on a nock at 5/8”, which I think gives me an almost perfect tune, all of a sudden my grouping just blows up. This happened exactly the same way on another bow one other time. Any ideas?