A buddy of mine installs home security systems, and he once spent weeks trying to figure out why a motion sensor kept going off in a client's living room. He replaced everything, checked the wiring, even thought the family pet was setting it off. Turns out, the client had one of those fancy art sculptures with a small motor that rotated it slowly. The sensor was picking up the heat from the motor or maybe the movement, I'm not sure. He had to reposition the sensor away from the artwork, and that finally stopped the false alarms. It was one of those things you'd never think to ask about during the initial walkthrough.

Totally overlooked how rain brings in all sorts of loose junk, not just mud. Lighter debris hitting the impeller makes a different noise than solid sediment. Colder rainwater can also make the pump housing shrink a bit, altering vibrations. Even small changes in temp or debris mix can throw off the sound big time. Next time it rains, see if the intake's clogged with new crap.

Speaking of awkward, @karen930, I once got my belt loop snagged on a nail. Had to do this weird shuffle and nearly left my pants behind.

Budget talks can be tricky (tell me about it). Try explaining that underlayment saves money long-term by preventing noise issues. Clients hate call-backs almost as much as we do.