They are good machines and not a lot to go wrong. Are you sure it’s 3ph, looks to be starting capacitor hanging underneath the motor connector box: looks single phase to me!
A few things to check. Take a few tools, imperial and metric Allen keys, flat and Phillips screw drivers, large open ended spanner’s / large adjustable spanner, Engineers square, white grease and access to a mortice chisel.
Initial just grab the head and table and give it a good wiggle. If it moves start by tightening the gribs up. Spray the ways with white grease and tighten up the gribs so the head / table still moves smoothly, just before you lock it up completely. Then do the following tests.
Take the back panel off the reveal the chain, see what condition it and the sprocket is in. Chances are it’s been greased when it should be oiled. It has grease nipples but they are for oil. The chain connects to a lump of concrete in the base. If the chain / sprocket is worn, easy to replace, just a cost.
Take the pressure off the chain, and see if the handle shaft has a lot of play due to wear. If it has walk away.
Place a mortice chisel in the holder and check with an engineers square that the mortice chisel is square to the table. Move the head to different positions (as well as operating the handle to move the head) and check again by slackening the big nut behind the Chuck.
The handle (big wheel in the front) pulls out, it should have a definitive indent you can feel when you move it between side to side and front to back movement. There is a ball bearing pushed by a spring that creates the indent. Can be worn, easy to replace, but it’s a cost.
With the head stationary, move the table to all limits and push down on the outer edge of the table and with the engineers square check all remains square to the mortice chisel.
If any of these checks with the mortice chisel fail, try retightening the gribs up. All axes have them. If you can’t get it to move smoothly and be square to the table walk away, it’s worn and the ways need machining.
If it fails the engineers square tests walk away the ways are worn and you would need to get them machined