Why is Cohen ON written with a vav the second time?
The first time, he gives his daughter to Josef (obeying Pharaoh) seven years later Josef does not marry Serach Bat Acher (because of him) and this failure by the high priest results in Egyptian famine. Had Josef replaced the priesthood, no such famine would have occurred! For those who don't accept that Alef Vav Noun is sin (since the spelling is ayn vav noun) please look at the Haftarah for Hanukka where the seven eyed stone (alef beit noun) appears by the word sin (alef ayen noun) and Cohen Gadol. This is not mere chance..but comes to confirm how central this lesson is for understanding this section of the Torah.