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Maybe measure your axle to axle length. String stretch can cause your grouping problems, too, and that'd show up by either a longer than normal draw length or longer axle to axle measurements. 1/8" makes a difference in axle to axle. But, yes, 8 years is a lot of shots for an arrow to recover from. Try your newer arrows vs. your older arrows, and that'll show you whether or not it's shot out arrows causing your problem.
I should Easton aluminum, Gold Tip carbons, and cedar (traditional).