Hey Sally,
I had a similar issue recently. One thing I found that sometimes gets overlooked is the pump basket and the shaft seal. Even if the filter looks clean, a partially clogged basket or a slightly worn seal can make the motor hum or buzz. Also, check that the pump isn’t air-locked, sometimes just loosening the pump lid slightly while it’s running can help release trapped air.
If all that looks fine, it could be the motor capacitor or bearings starting to fail. In my case, swapping out the capacitor fixed the buzzing instantly. Definitely try the easy fixes first, but if it persists, getting a technician to inspect the motor is the safest move, catching a motor issue early can save you from a full replacement later.
Also, as a side note, while I was at it, I treated my water with AquaDoc clarifier since the pump struggles can sometimes stir up fine particles, and it made the water crystal clear again in a few hours.