At sixes and sevens

London has a genuinely documented dispute that fits this phrase perfectly: in 1484, the Worshipful Company of Merchant Taylors and the Worshipful Company of Skinners argued so fiercely over which guild should rank sixth and which seventh in the City of London's official order of precedence that the Lord Mayor had to intervene, eventually ruling that the two companies would alternate the two positions annually, an arrangement that continues to this day. It's a wonderful story, but the phrase "at six and seven" already existed before 1484 (Chaucer used a version of it in the 1380s) with a similar sense of confusion or risk, likely from dice games, so the guild dispute may have reinforced an existing phrase rather than created it.