So that's why a 2 systems were getting crappy speeds. Yes, 2. It had been used only to split a single drop from another switch between two systems.
New drop, happy clients.
Some stuff here is museum material.
At least the lathe isn't running punch tape.
Don't upgrade or mess with the control. Disconnect from the network if it's on it. It should have RS-232. Throw a Pi or other SBC that does serial and a 12V level shifter; use that to feed it programs.
Also, make an image of the hard drive if it has one and start looking for a spare drive on ebay.