A report at TheSemPost from one of Google's Hangouts describes a situation where a canonical is incorrectly set up. Does it cause a problem? Google's John Mueller says, "not necessarily." Google's systems are pretty good at detecting when there's a significant error in the canonical implementation, especially when it's all pointing to the home page.

Read more about it http://www.thesempost.com/google-ignores-canonicals-implemented-error/