Yeah, sorry I didn’t update here, check the PTFE tube and clips for catching on the rear of the case, and for anything that restricts the head from moving all the way to the front corner. Easiest way is to turn the power off and manually push the head into the front corner, feel for any binding or restriction that happens right around where it should stop. The motors run at reduced torque during the homing process, so it doesn’t take much to throw them off from the actual end of travel.
The head should move freely to the end of it’s travel, these machines don’t use endstops or other confirmation of end of travel, they just run the tool head until it hits the end of travel and monitors the stepper motor backfeed for when that happens. IMHO, not a great way to do it, since it can end up wrong for the X-Y axis, having an optical or mechanical stop would at least allow them to CONFIRM that it actually reached the end of travel and wasn’t interrupted while still using the same system they do now for calibration.
Alternately, since they know the number of steps along each axis, calibrating against the back left, then the front right could be used to confirm that it’s actually reaching the end of travel in both axes, though I suppose that would add another 10 seconds to the process…