Factual error: Towards the end of the movie when Ally is in her hallway looking at Jack's old concert tour posters hanging on the wall, the poster closest to the camera says "Washington State Fair" and a 2011 date. Unfortunately, that fair did not get that name until 2013. Before that, it was called "The Puyallup Fair" (officially named the "Western Washington Fair"). Locals still call it "The Puyallup Fair" to this day.
Character mistake: Dumplin' is looking through her aunt's belongings, and finds an old application form for the Miss Teen Bluebonnet pageant. The application has an August 1993 signature but marks Lucy's DOB as 5/5/79 with a stated age of 16: it does not add up, as she'd have been 14 instead. Granted, it's an application she never actually turned in and not an official document, but this does not justify the mistake in the context of the movie (not to mention that had she just been too young to participate, the point of the movie would be moot).Sammo
Other mistake: As established in the original and this film, when the Admiral fires his cannon, everything in the house falls off walls and mantles, and everything needs to be caught to prevent them from being damaged. However, when he fires his cannon as Mary Poppins and the children are going out to have the bowl repaired, Michael has already left for work, Jane and Ellen are standing outside, and Mary, the children, are getting onto Jack's bike - leaving no-one in the house to catch the falling objects which would therefore all be smashed or damaged.