That amount of variation should be tolerable Jon. You mention that your motion is the most impacted when close to home, to me this would point to your X-axis anti-backlash nut perhaps not being fully aligned that it’s causing more noticeable friction as it nears the left bearing. What I’d recommend for that is to loosen the two M5 bolts, and then slowly alternate on tightening them when your machine is positioned right next to the left bearing to ensure they’re as aligned as they can be. Let me know how you find that to be