check X axis motor brake. check encoder and encoder link to control.
However, I would recommend double/ triple check mechanical points. I would move X axis full stroke forward - back rotating the ball screw by hand to be sure about mechanical condition.
some lathes are equipped with some kind "balance" mechanism for slanted bed. Don't know about this exactly model, but it makes point to check. The "balance" creates the force reacting against total saddle weight to make movement balanced and easier.