I've found not necessarily a solution, but at least a temporary source: Recently I added some Nuka World decorations to my settlement at Red Rocket Truck Stop- some Nuka Girl cutouts and whatnot. After THAT save, I could not go back to Red Rocket for the same CTD you've been experiencing. The save RIGHT BEFORE though, does not exhibit the same crash. I don't know why, but that's at least what I've discovered.