Silicon spray can cause galling at a metal to metal sliding contact. It is famous for destroying air guns. While you clean it out you can investigate the problem.

Can you feel excessive drag when you wind the slide screws by hand?

Are you blessed with an oscilloscope? You could check out the Arduino step pulse. Is it excessively up or down? A square wave is perfect.

You can get small amounts of slideway oil, no need to get the whole 5 litres.