The greatest plot hole in Fantastic Beasts: The Crimes of Grindelwald is the Elder Wand - but is there a way to fix it? Writer J.K. Rowling is one of the greatest authors of the present day, and she's well known for weaving together complex and sophisticated plots. Unfortunately, the Wizarding World has now grown to such a size that it's hard to keep track. The Fantastic Beasts sequel features a number of retcons that have taken fans by surprise, most notably the decision to shoehorn Professor McGonagall into scenes set in Hogwarts.
But, in truth, the worst problem of all is the Elder Wand. As Harry Potter and the Deathly Hallows revealed, the young Dumbledore and Grindelwald were obsessed with the Elder Wand. The two parted ways in heartbreaking circumstances, shortly after Grindelwald successfully acquired the fabled Deathstick, which is believed to be the most powerful wand in existence. According to legend, the Elder Wand is able to teach its users dark sorcery that has otherwise been lost in the mists of time - perhaps explaining the sheer scale of his magic in Fantastic Beasts: The Crimes of Grindelwald, when he unleashes a horrific attack that threatens the entire city of Paris.
Unfortunately, as powerful as the Elder Wand may be, it's also become an apparent plot hole in the Fantastic Beasts franchise. That's because the Elder Wand is unique among all wands; it has an "allegiance" to a master, and can only be claimed by another when that master is defeated. Harry Potter and the Deathly Hallows gave a sense of just how this worked. In the time of Harry Potter, the Wand was owned by Albus Dumbledore, and he aimed to take it with him to his grave. He was ultimately Disarmed by Draco Malfoy, who unknowingly became Master of the Elder Wand. When Harry knocked out Malfoy months later, the Elder Wand's allegiance passed on to him. Thus Harry Potter became the true Master of the Elder Wand, much to Voldemort's dismay.
Circling back to the 1920s, Grindelwald didn't wield the Elder Wand in Fantastic Beasts and Where to Find Them. From an in-universe perspective, he was impersonating Graves, and so would have had to use Graves's wand to maintain his cover; the out-of-universe logic, of course, was the fact that Rowling didn't want attentive viewers to deduce Graves's identity the moment they saw the Elder Wand in a trailer. But here's the catch: as Draco Malfoy demonstrates, you don't need to defeat a wizard while he's wielding the Elder Wand in order for it to switch its allegiance. You simply need to be best them. And, crucially, at the tail-end of Fantastic Beasts and Where to Find Them, Grindelwald is defeated. He's pinned by one of Newt's creatures, the Swooping Evil, and then disarmed by Tina Goldstein. Mastery of the Elder Wand should, therefore, have passed to Tina - the one who took Grindelwald's wand. That's clearly not the case in Fantastic Beasts: The Crimes of Grindelwald, though. The Dark Wizard swiftly regains the fabled Deathstick, and uses it to launch some of the most spectacular displays of magic seen in the franchise to date.
There is, however, one possible fix for this plot hole. It's safe to assume that the Elder Wand was created by a wizard who imagined it being passed down from one bloodthirsty sorcerer to another, by way of victory in combat. But how exactly does a wizard gain the Wand's allegiance? The rules seem fairly flexible, including everything from brutal murders to simple Disarming spells. One historical figure, Hereward, gained the Elder Wand's allegiance by locking his father in a cellar and leaving him to starve to death. But however these rules work, let's assume they don't allow victory via creature. The Elder Wand could easily consider Grindelwald already defeated by the Swooping Evil before Tina took his wand from him. In that case, it's conceivable that the Elder Wand wouldn't switch to a new Master.
Many of the continuity problems in Fantastic Beasts: The Crimes of Grindelwald are a matter of detail; McGonagall's age, for example, can only be inferred by combining a throwaway reference from one of the books with an article Rowling published on her Pottermore website. Indeed, there may even be story reasons down the line explaining why Rowling has changed her canon. In the case of the Elder Wand, though, the situation is a little trickier; a subtle detail in these films appears to contradict an important plot point in the established canon. There is a fix, but it's a tricky one, and it feels more like a way of explaining away a continuity gaffe rather than something intentional. It will be interesting to see if Rowling addresses this problem directly.