Clarify... Your groups at ALL distances are 3" right?

I'd have to ask what kind of lighting you were in when you sighted the bow vs the kind of lighting you were in when you shot those groups. If you sighted in under noontime sun and shot the goups in late evening, that could very well do it. You eye sees the pins differently in one kind of lighting than it does in another. Some sights are worse than others in that regard.