Green’s Dictionary of Slang

a blunder, a mistake.

1967		J. Hibberd White with Wire Wheels (1973) 225: Nothing annoys me more than bugger-ups like this!
1993		M.B. ‘Chopper’ Read How to Shoot Friends 122: The various stories that followed [...] were the last straw for Margaret in a haystack full of past bugger-ups on my part.