I’ve shimmed, I’ve squared, I’ve trammed. Why is my XCarve sooooo far off on the left than the right? I’ve surfaced the wasteboard so I guess it won’t matter too much at this point but what the heck? It’s a good 4mm off!
Try loosening the X rail on the Y plates and raise the low side or drop the high side or both. There may be enough slop in the plates to adjust. Measure before you re-tighten.
You can also add thin chipboard/cardstock shims between the waste board and the sub frame to raise the lower areas