When you run production, it first saves Photoshop's current history states and units setting. While production is running these are changed to zero history states and pixel units. At the end of production, it retores the original preference settings in Photoshop.

If the production process is interrupted for some reason, the setttings will not be restored at the end and you may need to do this yourself in Photoshop:

1. Preferences -> General -> History states
2. Preferences -> Units & Rulers -> Ruler (Units)

While this may occur while you are sorting out your Production setup in ProSelect, once this is sorted out, Photoshop should not be stopping and your setting should be restored correctly.