Harry Potter's narrative had at least one plot breaker, in my point of view (Maybe it's because J K Rowling went so deep into the magic narrative?), and I found myself doubting the entire history.
As pointed in various blogs in the internet, the plot breaker I'm talking about the Time Turner, used by the trio to save Sirius Black from the dementor's kiss in The Prisoner of Azkaban. I mean, if such a device existed, why was it not used from the start to destroy Voldemort in the very beginning of his existance?
I know How-It-Should-Have-Ended videos are far from being trustworthy references, but just to show my point,...
My question is: Is it a plot-breaker? If not, why? Are there others?