The most definitive reason that could make a source unreliable among the provided options is:
There is an inaccurate fact on a page of an article.
An inaccuracy can undermine the credibility of the entire source, as it raises questions about the validity of the information presented. Typos and non-expert corroboration might lessen credibility, but they do not inherently make the source unreliable in the same way that factual inaccuracies do.