The Taig mill with leadscrews uses two ball bearings on the driven side of each screw. These do wear out on occasion and need to be replaced. Two bearings are required per axis.
You might also want to pick up an extra ‘woodruf’ key. This is the half-moon shaped little piece that locks the dial/stepper coupler to the shaft. They can be hard to get out after years of service so having an extra or two on hand is a good idea. This is part #200-32, see link below.