Not that original then.

What stepper drivers are fitted?
A photo of the control cabinet would probably be good.

My thoughts to it having only recently started, is probably something starting to fail.
Probably worth a run around the control cabinet, making sure all screw terminals are tight, and unplugging and reseating any pluggable connectors, just to make sure there's no corrosion in any of them.

Then I'd probably be looking at the spindle motor, and the controller.