Factual error: After Lex Luthor and Deathstroke step out onto the deck of Deathstroke's ship, Ravager and begin talking, Aquaman's sub surfaces and smacks into the Ravager and it shakes violently and lurches. Yet the crew, Lex, and Deathstroke stand perfectly still just moving their arms around a bit. An impact on a ship like that would send all people standing up falling everywhere with no balance. (00:27:10)
Continuity mistake: In the beginning of the film when young Barry's mom is telling him about grandma's prayer, the shot of the side shows Barry's mouth is closed. But when it cuts to his face close up looking confused, his lips are parted and his teeth are showing. (00:00:35)
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.
Continuity mistake: During their fight, Aquaman gets off a good kick on Wonder Woman and sends her flying backwards. She hits the ground and starts sliding. She goes between two other Amazons before stopping. It cuts to a close up and suddenly the Amazon on her right that she slid past is suddenly where she has not slid past her yet. (00:59:45)
Continuity mistake: When Flash takes off running in the desert trying to test if he can break the sound barrier, the lightning bolt on his chest is much wider than seen just a couple of shots later. (00:42:55)
Continuity mistake: The bridge Lois hides under has several impact holes on the side of it from the war. These holes change in number and position in different shots of the bridge. (00:39:35)
Continuity mistake: While hiding from the Amazons under the bridge, Lois Lane hides by a purple car. There is an upturned blue car on the opposite side of the bridge there as well. This car disappears when the Amazons jump down to her and reappears again in the scene, also changing position a few times. (00:39:40)
Other mistake: In the flashback of Bruce Wayne getting killed, his mother is cradling his body and weeping. She has his blood all over her hand from touching his wound. She rakes her fingers across his shoulder and down his chest with her bloody fingers, leaving no trail of blood, but when she places that same bloody hand on her face it leaves blood all over her face and mouth. (00:35:05)
Continuity mistake: After fighting for a brief few seconds, Black Manta kills Deathstroke by burning a hole through his chest with his heat vision. Deathstroke falls right next to Lex Luthor as his chest sizzles and his swords fall around him to. A couple shots later as Black Manta is picking Lex up, Deathstroke's body and swords have vanished. (00:29:35)
Continuity mistake: On the deck of the Ravager, there is a large flak cannon that one of Deathstroke's men turns on Aquaman's forces. One of Aquaman's men destroys this flak cannon into a large ball of fire. Then a guy stands back up and turns into Clayface and begins absorbing some of the enemies. Orm uses his staff to obliterate this guy and behind him is shown where the cannon was. There is no fire, debris, or any sign of the destroyed flak cannon. (00:28:35)
Continuity mistake: Once Aquaman's forces begin attacking the Ravager, people begin dying left and right from both sides all over the ship. These bodies keep disappearing as the fight goes on. (00:27:30)
Continuity mistake: As Lex Luthor is discussing the shockwave epicenter with Deathstroke, he places his finger on the computer screen about an inch away from the Epicenter blip down to the left just as the orange moving blip begins going across the screen again. The orange blip makes it almost to his finger before it cuts to a close up of the screen. Now suddenly Lex's finger is much further away from the epicenter blip and sliding to the right, with the orange blip in front of his finger. (00:26:40)
Continuity mistake: After Wonder Woman snares Steve Trevor with the lasso and begins interrogating him, the other Amazons that were chasing him walk up in front of Wonder Woman. There are 5 Amazons there, including Wonder Woman. A few shots later when she's holding Steve up, a 6th Amazon girl suddenly appears with the other 4 that were in front of Wonder Woman, standing almost behind Wonder Woman but to the side. (00:22:40)
Continuity mistake: When Steve Trevor is running from the Amazons in the destroyed Big Ben, he leaps from a ledge and crashes through several boards on the way down as he shoots back up at the Amazons. When he hits, he rolls to his feet with broken boards all around him and several arrows hit the ground that the Amazons fired. When he takes off running and shoots back at them again, you can see the Amazons jump down to that very same spot before Wonder Woman's lasso catches Steve. The broken boards and the arrows have vanished. (00:21:55)
Continuity mistake: As Barry slides the grandfather clock to the side to get to the Batcave, a large plume of dust boils up around the top. It cuts to a view of this from the other side in the Batcave and there is no dust in the air at all. (00:20:30)
Continuity mistake: When Barry enters the Wayne mansion, he goes to a large grandfather clock to move it out of the way, gaining access to the Batcave. As he walks up on the clock, the glass on it has no visible imperfections except being covered in dust. It cuts to a close up of the clock as Barry begins pushing it aside and suddenly there are scratches and smudges all over the glass. (00:20:25)
Continuity mistake: Finally defeating her, Batman throws Yo-Yo down on the ground and she is on her side. One of her pigtails is draped over her head towards the back of her head. The shot cuts to Batman walking up to her and suddenly the pigtail is in front of her face. (00:16:20)
Continuity mistake: After falling down the stairs and seeing his mom alive, Barry stands up and turns completely towards his mother. The shot cuts to a different angle at close up, and he has to turn his torso towards her now. (00:13:25)
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)
Factual error: When the rest of the Justice League arrive at the Flash Museum, Captain Atom vaporizes a section of the wall to allow him and some others to enter. The hole shows 3 layers to the wall, the inner wall, the outer wall, and a middle apparently metal center section. There are several circle like spots around the hole in the center part of the wall. They are all perfectly round, despite being in any given direction around the circumference of the opening. This is wrong. The circles would be caused by structural bars inserted in the layer, and they would all have been either vertical or horizontal, and thus the circles would not be circles all the way around, but changing to elongated and shorter depending on where they were on the opening. Yet all are perfectly round. This would mean that the all the bars were in all different directions and converging in the center of where Atom just happened to make the hole, which would never be the case. (00:07:05)
Answer: Flash couldn't travel through time later in the movie not because Zoom was alive but because Zoom was also tapping into the Speed Force, preventing Flash from gathering enough of the Speed Force to break the Time Barrier. When Flash originally went back in time it's likely because Zoom was in custody, therefore not tapping into the Speed Force at that time.