Lost a full shift over a mislabeled part
Man, I just had the worst day. I was replacing a fuel line on a small plane, and the part number on the box was wrong. It looked right, so I installed it. Turns out it was for a different model, and the fit was off by a tiny bit. We had to tear everything apart again to check. That meant pulling panels and redoing all the connections. I spent hours on what should have been a quick job. Now I check each part against the manual before I touch anything. It's just so frustrating when something simple gets messed up like that.