Calibration question

[Hugues]

To add to the above:- when I look at my gcode with a gcode viewer, it's a perfect circle, so it does not seem to be a gcode, slicer or stl problem- I printed a 100mm circle today, it's pretty much circle, maybe a difference of max 1mm between largest D and smallest D- so the problem i saw with my small 15mm circle does not scale up, looks like I always have about 1mm-1.5mm difference, diagonally between X and Y axis. But I have no clue where can this come from