I just replaced my 3d printed proximity sensor mounts with aluminum. Anytime I would rehome for whatever reason I would have to re-zero the part sometimes it would be off by 5 or 6 thou. I knew it wasn't right because my router has the same setup and is repeatable to like a tenth. The issue has this disappeared with the aluminum mounts. I'm not sure if it was vibration or movement of the wires tugging them around. Something to think about.