When making a flat cutting surface the z axis seems to be tilted
Try remounting your spindle and seeing if you can adjust it out, if not your Gantry might be unevenly tightened.
I made a tool for checking it. I have in my “things” on thingiverse, Allted or mpcnc.
The larger the bit the more this will get magnified. My builds are usually within a 1/8-1/16 over a 6" radius with a bit of tape or a paper shim I can get it very close to perfect in a few minutes. Your looks to be drastically out.
Oddly enough the conduit has a thin flat line, rotating the conduit almost fixed all of it. Still some flexing in the Y part of the gantry but not sure how to tighten that up.
That is awesome, it means you have been using it!
On the Z axis one of the rails has some play to move around the other rail is tight. Any suggestions beside replacing that rail.
That is usually just an imbalance of tension in the gantry or your tool mount plate is skewed. Easiest to loosen everything as it is fully assembled and slowly and evenly snug it up.