NYArrow, Here's what I think FWIW. If you are shooting reasonably good groups with arrows of the same spine, then your form is consistent. Even if your arrows are two or three spine groups off, you should still be able to shoot groups. The groups may be left or right, high or low of the target but there will be groups. Until you are able to do this, you are "chasing your tail". You will never know if it is your form or the tune of the equipment.
In general, no groups = you, good groups, just not on target = equipment tuning.