So you used an ERD 4mm larger than the mfgrs spec and got spokes 2mm to long. That makes perfect sense, so I suspect that you somehow mismeasured the ERD. Is it possible that you factored the 2mm thickness of the nipple heads twice?
The other possibility is that you accidentally reduced the cross, oe calculted 3x, built 2x, but this usually causes a greater length error than 2mm.
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