Years ago.... clients on the other side of the word complained that they had moved the equipment we supplied from one room to another and now it would not work. Obvious thing was to check the recabling etc, I told them (via email) that the gray cable had to go on the first socket in the machine and because englis was not their first language I put 'number 1' in brackets.

Days went by and I found myself on a plane, a few planes actually and more than two days continuous travelling to reach their site. I went straight to their office and they showed me what they had done including the gray cable plugged into socket labelled '1', the only problem was the first socket was labelled '0'.

46 hours of travel to do a job that took 30 seconds then the same to get home again, but I did get to see a lot of movies that week.