Before adding a missing movie to an existing collection, we strongly recommend reading our general collection guidelines and checking the collection's change history.
Please do not re-add films (parts) that were previously removed by mods. If you think we made a mistake, please use the report button. You can also use the report button to ask mods to verify and lock movie sequels.
Getting a validation error while trying to add a new movie to a collection usually mean the movie is already in a collection. You can remove a movie from a bad collection if it is against the rules or a higher number duplicate, but please be very careful not to remove proper sequels from good collections. We might consider it sabotage.
Another possible explanation for a validation error is the movie entry was incorrectly converted into a collection. In that case, convert the bad collection back to a movie and follow these steps to create a new collection if needed.