It was my fault - I took the blame...
I was a lowly "IT Co-ordinator" (effectively just the guy the operators reported to), having spent a couple of years as operator myself. So, when I was elevated to the position, we got a new trainee operator who had zero knowledge of minicomputers or anything much beyond basic DOS commands (DOS 2.1, probably, in those days). I worked a week or two on shift with him and then left him alone to run the overnight batches, which consisted of (1) run backups (2) run day-end (3) print the invoices, then take them downstairs to separate and burst, ready for the day staff to stuff into envelopes.
All appeared to go well, at first. Then after his 3rd or 4th solo run, the sales people came to me about halfway through the morning to query why there were duplicate invoices (if memory serves, one duplicate of each invoice went to them for checking - turns out with good reason). Oh sh!t - dear Nicholas (his real name, why not, it was a long time ago) had seen me "BREAK" and "ABORT" running jobs, and decided to do the same with the day-end batch (a couple of times) because... who knows why, it probably seemed like a legit reason at the time. Entirely my fault for not explaining when I did it that some jobs can be re-run from scratch, others not so much.
We restored the backups and I think that instead of re-running the batch which would have taken the best part of the rest of the day we left it for a 'double day' run that night. Leaving the staff to re-capture the morning's sales orders and the mail room guys to stuff a double batch of envelopes the next day, but more importantly the company head office had to restore their backups from last night and re-run *their* day-end because our system had of course uploaded a munged version which they then processed. I didn't get much of a bonus that year.