I'm also using CoreXY kinematics, and I'm getting something similar. Homing works fine on min endstops, all 3 axes. Checked motion, and positive is definitely moving away from the origin. Origin is in the front-left of the print bed. In my case, when I attempt to use auto bed leveling, the head appears to move to the correct X position, but the Y position immediately maxes out and starts grinby EricL - Firmware - Marlin