@mentok - I assume you have BUG installed for Single-Player and you are trying to play a different mod. If that's the case, open that other mod's INI file using Notepad and change NoCustomAssets from 0 to 1.
Can you please post a save? I think this is available in vanilla, but with a save I can open it without BUG and double-check.
How do I make it so it ONLY LOADS when I ask it to, or with a save that was created with it(like the HoF mod)?
Mods = 0
BUG installs using 2 different methods. The first (recommended) way put BUG in the custom assets folder, this means BUG is loaded every time you play BtS. The second way is to have BUG install as a mod (the Multiplayer option). You want to install using the second option, as then BUG will only load when the BUG mod is loaded.I installed BUG...didn't know it would load on startup EVERY time!
How do I make it so it ONLY LOADS when I ask it to, or with a save that was created with it(like the HoF mod)?