Y axis not square

Been working on the Ole x-carve today, putting Robert’s Y axis plates on to stiffen up the Y axis. I noticed the Y axis didn’t seem to be square with the waste board. I moved the y axis all the way to the front, the left side x axis plate seems to be closer to the y axis end plate by 3/16s of an inch than the right side. I put a straight edge across the y axis end plates and they are square with each other. Not sure what the problem is… any help on this?

Check out these threads where similar issues were discussed: