Hey Russel, hey Pat, hey all,
true, that looks like damage exclusively from wood dust. A clear indication of inadequate dust extraction.
You know that not only these bearings, but also the ball screws of the CNC machine are incompatible with wood dust?
As you can see on the fan blades, the fan sucks the air from the back of the machine (this is always the case, also on air-cooled spindles). Usually you should have no wood dust there.
How do you extract the dust from your CNC machine?