@dmertz may be able to tell you where you went wrong. Turbotax should not even know about the after-tax 401(k) contributions ("Roth 401(k)") except as an item in your W-2, box 12 with code "AA". The fact that turbotax is reporting your Roth 401(k) contributions as excess Roth IRA contributions means you reported something in the wrong place.
