What a great system. One thing I am curious about. I noticed on mine a small bit of ‘play’ possible because of the two pairs of set screws that hold the Y tubes in the blocks - not much however. So theoretically if you loosened them all and pushed one set of Y blocks together, and pulled the other set apart, then retightened, I am guessing there may be a few mm difference in length. That could impact the squaring, but a small amount at best. I would be curious how close they are. Would you be willing to use your measuring system to see if there is variation in distance between your Y axis blocks (those connected to the same two tubes). I checked mine and they were the same (but I only have a standard tape measure, so by eye they looked to be the same distance apart).