Today a student of mine pressed an arrow key to nudge an object, and was sent back in her history MANY steps. This occurred seemingly at random, repeatedly, and always to the same history state. Even *after* quitting photoshop completely and reopening the document. Does anyone have any insight into why?
This was CC2019 on a new MacBook Pro running Mojave.
How did you go back ANY history states after closing and reopening? It doesnt save the history in the file, so there is no history states to go back to. Or do you mean you repeated steps and it did the same thing again? If that is the case, was she hitting only an arrow key, or was there any other key hit at the time? Was an actual layer selected in the layers panel or were they highlighted on something in the history panel and "nudging" through their history?
It remembered the file’s history even after quitting and relaunching, which definitely isn’t supposed to happen, but it seemed to anyway. A layer was selected along with the move tool, and she didnt press any additional keys.
Wow, that is different to say the least! Have you tried it with the same file on a different computer to see if it does it there as well? If it does, you need to contact Adobe directly because that is one crazy anomaly. If it doesn't happen on another machine, I would say the easiest thing to try first is to reset the preferences in Photoshop. If that doesn't do it, I think your best bet would be to uninstall photoshop and reinstall.
In case you need help resetting preferences...
1. Open the preferences window.
2. Click on the General tab
3. On the right side of the window, toward the bottom, there is a button that says "Reset Preferences on Quit", click that.
4. Close down Photoshop, wait a few seconds and restart. Then see it it helps.