This usually means the manual mod is outdated or conflicts with the current game version (e.g., the "Spaced Out!" DLC vs. the Base Game). Delete the folder from mods/local to restore game stability.
Some mods require the ModUpdater or PLib library to function. Check the mod's download page to see if it has "dependencies" that also need to be installed manually. Why Install Manually? oxygen not included how to install mods manually
While the Steam Workshop provides a "one-click" solution, manually installing mods is essential for players using the Epic Games or GOG versions, or for those wishing to manage specific mod versions locally. This usually means the manual mod is outdated