I find that if you pause and stop the spindle to change a broken bit or some other reason it was often difficullt to return to the exact same spot.
I bought a small laser pointer (a dollar store toy for cats - they chase the spot of light) and taped it to the side of the spindle extrusion. When the X-carve stops I turn it on and mark the spot on the spoilboard with a pencil where the laser shines.
I also mark a home reference point for a project’s start so if I have a stoppage and the cutter returns to home that I know it returns to the same spot, or can be returned to the same spot either with the control arrows for “X” and “Y” or manually.