Install the game + any DLC to your internal hard drive and play without your external storage plugged in. For this reason, it is best practice to unplug your external drive before you go to install OR play any modded game. It seems very random, sometimes it happens soon, other times you get 120+ hours into a playthrough and you come back to no mods suddenly. It is not a question of IF, it is a question of when.

So having your game installed on an external storage device, and having the mods always install internally, means that at some random point down the road, your mods will disappear. Mods cannot be saved or transferred to an external device. When playing ANY modded game on your console like Fallout 4, Skyrim etc, it is not recommended to use an external storage device to store your game.

Q: Is it safe to install Fallout 4 on my external hard drive? Ī: No. ~ Welcome to Fallout 4 Mods ~ Modding FAQ