These priests ⌞couldn’t prove they were Israelites⌟: the descendants of Hobaiah, Hakkoz, and Barzillai (who had married one of the daughters of Barzillai from Gilead and took that ⌞family⌟ name).
Next to them Meremoth, son of Uriah and grandson of Hakkoz, made repairs. Next to them Meshullam, son of Berechiah and grandson of Meshezabel, made repairs. Next to them Zadok, son of Baana, made repairs.
These people searched for their ⌞family⌟ names in the genealogical records, but their names couldn’t be found there. For this reason they were considered contaminated and couldn’t be priests.