There is a bug affecting every model I create. It's really inconsistent. Sometimes when I undo or smooth, or turn symmetry off, it corrupts my mesh and is irreparable. It basically causes he mesh to have zero width on some part of it. I can't even undo to reverse the changes and hope to god that I have saved a recent backup. See attachment to view what happens. Notice the top part of the model's head that looks like its see through and pixelated almost.