All of a sudden, people are beginning to talk about JK Rowling more like she's George Lucas than JRR Tolkien. After heavily revising and fleshing out her own lore over the years - including with the huge information dump that is Pottermore - she's now releasing material that directly contradicts things she's said or written in the past.
It's all well and good adding the details that Dumbledore is gay or Nagini used to be human, but when you start rewriting things to create plot-holes in your own beloved material, there's a problem. That counts doubly when those stories were ALREADY full of plot-holes in the first place.
In short, it's pretty fair to say that The Wizarding World is now more riddled with plot-holes than Hogwarts is with nargles...
15. McGonagall At Hogwarts?!
When fan service goes wrong, it's unforgivable. Particularly when it's thanks to a writer not paying attention to their own details, which is very much the case with the plot-hole opened by Minerva McGonagall's cameo in The Crimes Of Grindelwald.
We see her briefly at Hogwarts and she appears to be around her mid to late 20s or so, which makes absolutely no sense. She's appearing as a teacher at the school in 1927, despite the fact that she was born in 1935 (according to the bio now mysteriously deleted from Pottermore) and didn't start teaching at Hogwarts, in her own words, until 1956.
And before you say it might be a different McGonagall, the script confirms it's her (her mother's surname was Ross anyway).
Not only that, but it means that Dumbledore is presumably going to kick her out of a job, since he's been removed from his Defence Against The Dark Arts role and will become professor of Transfiguration.