The Cursed Child shows Harry struggling to relate to his son, Albus, and the entire play unfolds because of a fight they have. Harry goes so far as to tell Albus that he wishes he weren’t his kid, creating a much bigger problem than all the obvious retcons.

Even if Harry had angry outbursts at Ron and Hermione during the original story, he never said anything so hurtful to those he loved. Additionally, Harry would never treat his family poorly after the way the Dursleys treated him. A Cursed Child movie would need to alter this somehow, but that would create more issues for an adaptation.

A movie adaptation of Harry Potter and the Cursed Child would need to make Harry’s treatment of Albus more believable, but this would create a plot problem. After all, Harry’s words are the catalyst for Albus’ journey, and it’s unlikely his son would rebel to such lengths if his father treated him differently.

With that in mind, a Harry Potter and the Cursed Child film will need to find a new way to kick off Albus’ adventure. This isn’t impossible, but it will require a new approach to the script and altered emotional stakes. Changing such things is risky but necessary to set the sequel up for success.