Did you do a physical check of the impellor and motor? Look for scoring on the impellor or inside the motor. If theres physical damage, replace the units. If not, try soaking them in vinegar a bit to remove any hard water deposits and give it a good scrubbing. If that doesn't work, make sure that the shaft in the motor isn't bent, the ends are properly secured, and the impellor will freely turn by hand. I never had an impellor or motor go bad on anything except aquaclears. I have old whisper filters that still work from 25 years ago. SMH.
Sometimes motors that have been running for years have a hard time working once they have been stopped for a little while. A thorough cleaning is usually the answer.