Spent the last 3 hours investigating an issue at work the client raised.
Spent 2.5 hours meticulously reviewing and fixing the issue thinking it was our fault and trying to figure out what happened.
File was 10,000 lines long.

Then once I had made all the fixes and still unsure how it happened and just about to send an email, I went to the original file and found it was not us but them!
Feel so much better as they were attempting to say it was us without thinking it was self inflicted.
Anyway sent a new file with corrected info including errors they did so feel much better even though I had to work back very late.
Just call me Sherlock.