bit rot is your second paragraph. zfs has ways to handle bit rot in hard drives as an example. Not sure there's a word defining what you mean. Sounds like some

bit rot is your second paragraph. zfs has ways to handle bit rot in hard drives as an example. Not sure there's a word defining what you mean. Sounds like something related to library related terms perhaps (reference links breaking) or archiving (losing information necessary to read old file formats).