Revealing mistake: During the flashback when we see Bruce Wayne murdered, Thomas Wayne is beating up Joe Chill while in the background, Martha can be seen cradling Bruce's dead body. As she picks him up though, the animators forgot to remove the still frame so it appears as if there are two corpses.
Revealing mistake: After the museum battle, Barry wakes up at his work and looks at the computer screen at an article reading WORLD FACES ARMAGEDDON. Look closely at the blocks of text under it. It is the same lines of text repeated over and over again. (00:12:10)
Revealing mistake: When young Barry walks into his house and discovers his mother's murder site, he drops a book on the floor and a birthday card falls out. The book opens when it hits the ground and is towards the middle of the book, yet the pages are completely blank. (00:01:35)
Revealing mistake: In Flashpoint Batman's first scene, he is shown fighting Yo-Yo. At one point during the fight she wraps a rope around his neck and tries to strangle him. At the end of the fight, he takes the rope off his neck. The rope goes through his neck when he does this. (00:16:20)
Revealing mistake: Barry is handed a file at his work. He starts reading it but the paper is totally blank. (00:12:35)
Revealing mistake: When Lois Lane jumps into a trench whilst she is being chased, there is a vertical lined zip on her jacket. She turns her head partway and the vertical shaped zip on her jacket disappears for a frame or two. (00:39:10)
Chosen answer: Despite the ending in Flashpoint to indicate a Darkseid invasion, War is not a sequel. It's a reboot. While both films were part of the DC Universe Animated Original Movies series, War is the first movie of the series that is now part of the DC Animated Movie Universe. This is also why the voice actors are different.
Bishop73