I pulled it apart and there's nothing that stands out to me as a problem (not that I'm any expert.) The brushes have plenty of life left and I don't *see* anything wrong with the armature but I don't really know what I'm looking for either.
I might just spring for a new motor, I feel like this vacuum is worth it.
It's the 4424240 motor if that means anything, and the vacuum's model number is S312i. The tag has 1999 on it so maybe that's the mfg year.