Green’s Dictionary of Slang

a quandary, a state of confusion.

1916		‘Sapper’ ‘The Motor Gun’ in Men, Women & Guns 46: ‘Lord! it's a rum box up.’ He sighed wearily.
1924		‘Sapper’ Third Round 633: Good Lord! what an unholy box-up.
1988		McGill Dict. of Kiwi Sl. 20/2: box up state of confusion; eg ‘It’s a total box up, nobody seems to know what his position is, or what he’s s’posed to do.’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].