@realcaseyrollins@counter.fedi.live was talking about "canon" in a movie series (Marvel / Spiderman). Not long ago, #sonOne was talking about how he only accepts the original Star Wars trilogy and the newer movies (not the prequels) as canon.
Thinking about it, I don't know if "canon" is an adequate way to look at it. Each "universe" has multiple characters, each with their own unique point of view. Each character's POV will also change over time. So minor conflicts and sometimes even major conflicts between stories are consistent with telling each story from the POV of one character in said universe at a particular point in time.