A rather odd problem arose yesterday. I was trying to add a Motion Blur filter to an image. (Photoshop CC2018 - MacBook Pro Retina, 13-inch, Late 2013 Sierra 10.12.6 16G1036) Suddenly the image tilted about 30degs to the right. Nothing I could do would change this. There was no action in the History to undo. Even stranger, when I tried to straighten it even the Guides come down at that angle.
Pressing esc also works to reset it.