ednisley
(Ed Nisley)
3
You can check it with a framing square or a rafter square; pick the biggest one that will fit inside.
The gantry looks like it has two Y axis belts, so perhaps one is misplaced by a tooth on its drive gear, as in this larger CO₂ machine:
It’s not obvious to me if that applies to the CoreXY drive on your machine, but something similar may be amiss.