I’ve been working on this outfit using Mirror Modifier, Subdivision Surface, and Displacement (for collar).
This afternoon I turned off subsurf in the viewport, and discovered that several faces have this strange distorted shading…
I applied Rotation and Scale.
I used Merge by Distance and Recalculate Normals on the entire mesh.
I used Flip Normals on the affected faces. When that didn’t work, I deleted the faces, filled the entire area, then joined the applicable vertices.
I switched off the Displacement modifier just in case, but not surprisingly, it didn’t solve the problem.
Does anybody know what’s causing this, and how to fix it?