Steam sometimes corrupts large .ba2 archives during updates. To fix:
If you already own the DLC or are willing to purchase it, here is how to manage the files for a better experience: fallout 4 dlc files download better
If you are looking for a "cleaner" file structure without Digital Rights Management (DRM) interference: Steam sometimes corrupts large
Steam generally handles DLC well, but sometimes they fail to auto-download. Fallout 4 in your Library. Select Properties > DLC. fallout 4 dlc files download better