In university, we had to complete weekly tasks. A few times, the validation script provided by my professor returned an error, meaning that my solution had a mistake. When I tried rerunning the script the following day, my answer was accepted. At the end of the last lecture, my professor came to me and told me that I was usually the first one to hand in a solution and that he sometimes used my answers to validate his results.

Build caches are a bitch.