An example of this is the Potara time limit. As far as I know, there was never any indication of why Vegito's fusion was undone. I believe there was some dub or whatever that mentioned Buu's magic body, but that wasn't part of the original dialog. Yet it stuck for years and years until Vegito's second appearance for a canon reason to be given.
But people still call it "the potara retcon". Whether or not the explanation is good or bad is up to each individual's opinion. But not a retcon.