Reset Matrix Mirror Axis

I need help; when I add a new primitive, and hit mirror, it’s completely skewed. It’s off center and diagonal, and I have no idea how to fix it; all three axis are skewed, the model is in the center and the symmetry works fine on it, but for so,s reason mirroring primitives is broken; I noticed this change after I did a uv map to export to procreate; I don’t remember moving anything else and it worked just fine before: I can’t find a single tutorial on resetting this so it mirrors like it used to.

The image is just me addding a new sphere and hitting mirror; this is how it ends up.the model is at world origin

If the model has good topology and you want to mirror it perfectly I would use the mirror modifier in Blender with the Bisect option.

If you don’t mind remeshing again, you could move the object to the origin, rotate it with the gizmo (vertex mode) until it’s kind of ‘aligned’ and then bake the transformations (and mirror left to right + remesh again)

That’s what I do whenever I lose the symmetry (for me it’s the easier way to fix it).