Cosa Number Blunder
The Cosa Number Scandal was an error in the numbering of successive Cosas that occurred in official records between 1997/XVIII and 2001/XXII. Due to an error by Charles Sauls, newly-appointed Secretary of State at the time, the second Clark of the 23rd Cosa was marked as the first Clark of the 24th Cosa. Sauls compounded this mistake twice more later in his year-long tenure, with his last Clark as Secretary of State erroneously marked as the 5th Clark of the 26th Ziu, rather than the 6th Clark of the 23rd..
The error went undetected until noticed by a later successor, Marti-Pair Furxheir, who engaged in extensive detective work to identify and solve the problem.