One of my users sent me a save file with a FO4 bug where Preston and Codsworth cannot be assigned to any tasks in the settlement or even commanded via the workshop interface: http://www.filedropper.com/companionglitch (Preston is located in Sanctuary Hills and Codsworth at Red Rocket)

I've been having a hard time figuring out how to fix it. My theory was that one of their factions got stuck somehow and the workshop interface thus rendered them ineligible to command. However I've checked just about every possible faction and everything seems normal. I've tried other things too, like disabling and then re-enabling them, sending them to other places, etc.

If anyone has any idea why this is happening, I'm all ears.