Ok, I managed to figure it out. It wasn’t the redirectors not saving, however that is what appeared to be happening.
For the benefit of others, for some reason those specific BP’s when changing their folder location caused the default game instance class in the project settings to revert to GameInstance. Not sure why, but since I have a custom game instance all my BP function library routines that referred to it failed their Casts, which cascaded down through the game.
Weird one, but fixed. Any idea why the default game instance would suddenly reset? I had no made any changes to my custom GameInstance.