Axes flipped mysteriously in Sculpt Mode!

I was mid-sculp when I realized my mirroring had suddenly turned weird. I had to change mirroring the X axis the Z axis to get back to my normal X axis mirroring behavior. But this is only the case for sculpting. Translating, rotating, scaling, object mirror modifier, and all gizmos remain normal.

I reloaded, restarted and rebooted but the problem persists.

Any ideas how this happened and if it can be corrected?