That is fairly annoying, isn't it

Now some guys swear that the spindle will overheat with too much lube, but I'd be inclined to think that that dry sound indicates a lack of lube, if the bearings are/were actually good to start with. Do you get some visual indication of oil making it through the spindle? There should be an occasional drop or two on the spindle keys in the morning before startup. You could also remove the bottom spindle cap and see how oily it is, as some accumulation may exist there if it does not all get blown past the labyrinth.

Check for oil leaks up on the hoses from the air mist lube pump up top. Run the tests to see that oil output is correct. IMO, there is precious little oil being dipensed to the spindle, and any leaks or drop in oiler output are intolerable.

Have you tried to force an overlube condition by manually actuating the oiler a few times at the back of the machine? You can always run the excess oil out with the warmup program later, if you can get it to shut up.

On a long shot, you could also play with the belt tension to the spindle pulley just in case it is excessively tight, enough to affect the top spindle bearing (the floating bearing) somehow.

BTW, when I did my own spindle rebuild, I discovered the preload was gone on the lower bearings. So some of the noise I had could have been due to bearing race slippage there, as there was evidence of rotary wear on the end of the races where they met the preload collar.

I also installed a pair of super precision bearings up top, where one would think they are not normally required. You can't have too much precision, but you can have too much money