Continuity mistake: After Batman shoots Reverse Flash through the head, Flash rushes over to Batman and catches him before he falls over from his wounds. As Flash is lying him down slowly, there is no blood on Batman's face. It then cuts to a close up as Batman reaches up to pull off his mask and there is suddenly blood on his lips and chin. (01:12:20)
Continuity mistake: After Aquaman finds Orm dead and sees the carnage of the battle, Wonder Woman comes up behind him and stabs his back with her sword. He falls to his knees and she walks around in front of him, and as she does you can see there is no blood on her sword. But then she holds the sword to his neck in a close up and suddenly the sword is covered in Aquaman's blood. (01:10:15)
Continuity mistake: After dodging a low attack, Wonder Woman jumps into the air and slashes down at Aquaman with her sword. Aquaman raises his trident and blocks the attack, but is only holding the trident with one hand. It cuts to a close up and instantly Aquaman is two handing the trident. (01:00:25)
Continuity mistake: After catching the rocket and saving Cyborg and Batman from it, Superman turns and drops the exploded rocket and begins lifting into the air. It cuts to a wide angle as Superman is hovering above the ground, and the rocket he just dropped is nowhere to be seen. (00:52:05)
Continuity mistake: When Barry is looking at the gun case in the Batcave, a cork board is visible in the background covered in raggedy playing cards. The one to the left of the center Joker card has blood on it, a lot of it around the bottom right corner of it. Later when Batman looks at the cards, the blood on that card is significantly less. There is also a card to the right of the Joker card that is torn with no blood on it. But in the close up when Batman is looking at it, that card now has a large blood spot in the center. The card symbols on the cards are also closer together, the cards above the Joker are significantly less damaged, and change from suit of hearts to a different suit. The entire board seems different. A few shots later, the cards above the Joker card are back to hearts again. (00:20:45 - 00:25:30)
Character mistake: One of the top most taboo things for a super hero to do is reveal any aspect of another hero's identity to someone, especially a villain. But when Flash is trapped by the gray adhesive and the other Justice League members are about to take the villains away to disarm the bombs, Flash tells Green Lantern "Hal, go", calling Green Lantern by his first name right in front of Mirror Master. (00:08:05)
Continuity mistake: When Wonder Woman is interrogating Steve Trevor, other Amazons are standing around her. Between shots when another Amazon appears, some of the Amazons' sword sheaths and other items on them change coloration. The one on the far right first has a gray sheath with a yellow tip, which then changes to solid yellow. Her collar also changes from yellow to black. And the one closest to Wonder Woman has a sheath that goes from a gray with yellow tip to a solid gray. The Amazon closest to the camera also has a quiver for her arrows. It changes from yellow to brown. And the one between the one with the yellow quiver and the one on the far right is wearing a white skirt with a black band around the waist. The band turns yellow. (00:22:40)
Continuity mistake: Wonder Woman tries to stab Captain Thunder with her dagger and just breaks it on his chest. She then has to drop the broken blade to catch his fist as he tries to punch her. She then uses both her hands to use her Lasso of Truth to make him say shazam and break his form. The lightning bolt hits her and she flies off him as he reverts back to 6 children. As she stands up, the broken dagger is suddenly in her hand again. (01:08:35)
Continuity mistake: Just after Wonder Woman and Aquaman argue a brief moment about her killing his wife, they continue their fight. Between the close up and the far shot, the rubble by the wall they are next to changes significantly in shape and amount. (01:00:20)
Continuity mistake: On Batman's plane, Flash walks up to Batman's seat, places his left arm on the top of it, stretches out his right arm to the side and says "Bruce's Batplane was a little more... stoic." It cuts to a close up of Batman and suddenly Flash's right arm is crossed with his left arm and his hand on his arm. It is still like that when it cuts away again. (00:55:50)
Factual error: Superman begins shooting his super intense heat vision at the soldiers attacking him and the other heroes. His vision cuts boats in half, and incinerates the soldiers into ash in an instant. The lasers from his eyes are super strength, with him not yet knowing how to hold any of it back or shut it off, and it is going through the soldiers and boats. Yet the vision leaves no damage at all to the ground the soldiers were standing on, nor does it create any steam when going across the water cutting boats in half. (00:52:15)
Continuity mistake: Batman and Cyborg have their backs to the tunnel they just came from and are shooting at the boats in front of them. Some soldiers come out of the tunnel behind them and fire a rocket in their direction. Superman suddenly jumps in and catches the rocket and it explodes. The blast knocks Batman over the rock he was hiding behind so he is on the boats' side of it, not the tunnel's side. But moments later when he is getting up and twp solders are rushing him, he is suddenly back on the side he came from, just before Superman vaporizes the soldiers with his heat vision. (00:52:10)
Continuity mistake: After rescuing Superman, Cyborg, Batman and Flash step out into the open and are quickly confronted by several heavily armed boats full of government people. There are boats in front of the four of them and none to the side. But when Cyborg steps forward saying he can resolve this peacefully, two boats suddenly appears to their left slightly behind them. Then when the shooting starts, those two boats vanish. (00:51:10)
Continuity mistake: When Flash, Batman, and Cyborg walk into the cell that is holding Superman, a shot of just Superman's legs show that they are down with his knees on the floor. It then cuts to an angle from the trio and suddenly his legs are bent up and his knees in the air. (00:49:35)
Continuity mistake: Wonder Woman stands on top of Captain Thunder and uses her Lasso of Truth to force him to say Shazam, breaking his transformation and turning him back into the 6 kids. This causes lighting to come down and strikes Wonder Woman, sending her flying and sliding across the ground. When she comes to a stop, her hair is draped over her head. The next shot, she begins lifting her head and her hair is suddenly behind her head down her back again. (01:08:55)
Continuity mistake: While walking through the sewers, Flash is holding up Superman and beside Cyborg. Cyborg tells Superman that there are heroes, and Superman looks up at him asking "Heroes?" The next shot is from a different angle, and Superman is suddenly looking down again. (00:50:35)
Continuity mistake: As Batman makes his entrance into the Flash museum, he does so by busting through a skylight window. As it breaks and he somersaults down, you can see a load of large chunks of glass and metal framing falling all around Batman. But moments later when he lands, only a few small shards hit the ground around him. (00:06:50)
Plot hole: After Reverse Flash saves Lois Lane and kills all the Amazons that were attacking her, he disappears, just before a group of resistance fighters shows up. They know that they didn't take out any of the Amazons, it's obvious that Lois didn't kill them, yet the resistance members show no concern as to who was responsible. The war involves three separate groups, the resistance, the Amazons and the Atlanteans, each of whom is equally hostile to the other two. As such, the resistance cannot assume that whoever killed the Amazons must be an ally and let their guard down, as it could easily have been an Atlantean force, who would make no distinction between the Amazons and the resistance and would attack them on sight. An experienced resistance team would not be so casual about the situation. (00:40:50)
Continuity mistake: As Cyborg is opening the door to Superman's cell, several layers of blast doors open one at a time. The last one to open you see for a moment as it begins to slide, you can see the room beyond through it in red. It then cuts to the other side and suddenly there is yet another layer of door that is opening by just sliding to the right, preventing any possibility of a view seen less than a second before. (00:49:30)
Continuity mistake: When Reverse Flash stabs Flash in the leg with a piece of rebar, Flash is on a small pile of rubble. He takes the bar out and drops it on the rubble. But then it cuts to a different angle as Reverse Flash continues to assault Flash, and suddenly Flash is in a different location, with no piles of rubble in his immediate area. (01:04:50)
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.