Take the story of Lucifer. In the various texts, it is actually referring to a Babylonian King and then through the story has varied in interpretation.
This causes problems with the canon of the Biblical story and because so little of the original text is known, the differences in interpretation can become manifest in outright contradiction. Indeed, even when we have original texts, there are outright contradictions:
This makes it near impossible to determine the original intentions of the authors of the text - which usually isn't a problem, but the intentions are vital to determine the meanings of Biblical (and extra-Biblical) works.