After opening the bottom cap, where I previously trying in 2 metal washers, I put a tiny black grubber gasket under the washers to deaden the noise. MOST IMPORTANTLY, I find a rattle coming from the metal arm UNDER THE plastic barrier cover. I cannot get in there easily!!

I bend a tweezers so I can curve the gasket into place from the other side of the plastic barrier, clamp a black gasket into the tweezers with a rubber band, cut the gasket so it can be placed around the rattling screw from the side. No I use lighting and glasses to see the tiny workspace.

I put gorrilla glue on the gasket , hoping it will stay in place and then I push it into the gap between the metal arm and its holding screw. I use a curved pointed plastic all to push teh gasket off the clamped tweezers and onto the arm-mount-screw to leave it in the right place.

The noise is gone. I have put 2 gaskets into the fan. Super silent. This fix took years to formulate. I tried about 4x over 3 years. Thanks for reading, I hope you appreciate that I stuck with it.

2022 Update: I had to take these out because the fan stopped rotating correctly. The noise, however, is gone and the fan operates silently again.