One thing to check closely is the leadscrew. If it has been used for power feed taking heavy cuts it may be badly worn. That was the problem with one I had for years, In those days Clausing sold replacement parts. I replaced the screw and half nuts and used it for many years with no issue. My son now has it and still no problems. I told him "if you can't feed it easily by hand don't use the power feed".
Right!
Well, I don't even see it marked as SOLD! He must have sold it and took the ad down.
IDK if you all remember, but I've mentioned all my stuff is in storage ATM, including a Mongomery wards version of a Logan 200 10" lathe.
He did say the 618 had "wear". Where I don't know.
Nice thing about the Logan (lf l ever get it here) is l did a wiper motor PWM and ~ 12 V power supply, feeding my lead screw,
Only need to manually change gears if l need to thread. So l have a nice variable speed. reversable lead screw, with plenty of torque.