> Thank you for contacting us with your inquiry.

> The text of our Targum Onkelos is from Chumash Toras Elokim (Vilna, 1874) which includes R' Wolf Heidenheim’s text of the Targum; that text is based on manuscripts and is considered מדוייק.

> We appreciate the opportunity to clarify this.

If someone has this version please verify.  I'm not marking this answer as correct because it doesn't explain the underlying reasons why Nachshon is different than the others.