How to fix a squealing cadet wall heater?

Query by WaGirl: How to resolve a squealing cadet wall heater?
We have a more recent cadet wall heater (2005).
We have cleaned them numerous instances but one of them keeps squealing when the fan spins intermittently. Is it protected to include any type of oil to keep that from happening? Or does it want to be taken apart? I'm just a housewife and never know much about these things.
Many thanks for any input.
I indicate to say the fan spins but it'll squeal like rattle off and on.


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