I've been having this issue for a few years on many versions of Photoshop and many different machines and Mac OS versions. When on either of the full screen modes, if I'm doing any operation involving handles (transform, rectangle tool, etc) once the handle comes near the screen edge, the canvas will suddenly lurch away from the screen edge so quickly and drastically that my operation gets screwed up, and I have to start all over again. I can see why the canvas would move, so that the transform handle is still visible on screen, but it should do it gradually along with my mouse/pen motion, not in a sudden extreme shift. This doesn't happen every time, but quite often it does, and I can't figure out why. I believe there was a time when this didn't happen, maybe 4 years ago or more, so I'm not sure why it is happening now and has never been addressed.