The Whisper 5 filter chattering away behind me is the same one I've had for over 20 years.
The impellers are built badly on them. Every now and then you have to pull one out, put a dab of epoxy on it and let it cure, and then drop it back in. Right as rain for 10 more years or so.
I don't think they make these anymore.
I've stopped repairing them. Now I am getting rid of them through attrition since the local shops no longer carry pads for them. Only one left now. When it goes, I'm building a closed loop system with DIY parts.