Hi together,
I just stumbled over this video here: (YouTube)
Within the video the creator explains how the belts are slightly missaligned and how on his printer also the squareness between the reference-points is off.
And how to fix it.
As CoreXY systems are pretty picky when it comes to belt tension and alignment I could imagine that this is a possible solution to get at least some of the issues sorted out. (Espacially my issue with different deviation in X and Y axis).
I will give this a shot in the next couple of days.
If someone finds the time to try it earlier: please share the results.
BR
/Kevin