Your installer had a long day - a few emergency calls had to be handled. Getting all of the scheduled replacement work completed was tough, but it all got done.
The next day a customer calls with a complaint about a circuit breaker that keeps tripping. Maybe the installer hooked up the wiring incorrectly. Maybe it was something unrelated to the installation. To be safe, you send the installer back and, sure enough, he made a mistake on the hookup.