Thats' the one.
The X/Y saddle has dovetails machined presumably!! at 90 degrees same as the X2.
I am trying very hard to see how the X and Y can be out of square, it's also very difficult to do an actual
measurement of the complementary dovetails on the saddle to check their squareness.

The gibs were nice and tight and threadlocked and the steppers had an easy life moving the table (3Nm) . Table also had
no more than 0.08mm play with the X extended to far right/left.

I should of noticed this problem about 10 months ago.