Does anyone use the parallax method to focus? This is where you have a clear spot in center of groundglass that you mark an x with grease pencil. Then with a loupe you focus on something and move your head sideways. The image is in focus when the image doesn't move in relationship to the grease pencil x as you move your head.

Just tried this trick on a 35mm RF camera that I suspected of being out of whack, and sure enough it was wacked