Revealing mistake: Barry is handed a file at his work. He starts reading it but the paper is totally blank. (00:12:35)
Continuity mistake: After opening the door at his mom's house, young Barry is shown in a close up of his face. A white fence is seen behind him with red bushes all around the front of it. Moments later when the camera is pulling back in a different shot to show his mother's corpse, the same fence is visible, but now with no bushes in front of it. (00:01:25)
Continuity mistake: At his mother's grave after his wife tells him he was just a boy, Barry Allen raises his right hand and says he might have been able to stop it. There is no ring on his hand at that point. Then when he takes off running after his device alerts him to a break in at the Flash Museum, there is suddenly his ring on his right middle finger, out of which he pulls his costume. (00:02:40)
Continuity mistake: There are some large cracks on the wall left from when Captain Boomerang pinned Flash to the wall for a moment. When the gray adhesive traps Flash against the same wall again, the bottom most crack is to the right of his head. Then when Flash begins vibrating his arm to throw the adhesive and the bomb at Reverse Flash, the crack is suddenly on his left side. It switches back and forth during the scene. (00:05:00 - 00:06:25)
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: Reverse Flash knocks Flash back and he is next to the edge of a building, his arm hanging over the side. Flash sees Grifter get killed and tries to get up, but Reverse Flash presses him back down with his foot. Flash is still right next to the edge of the destroyed building. The Reverse Flash zooms around behind Flash, and suddenly there is at least a good 2 feet between Flash and the edge. Moments later, Reverse Flash kicks Flash and he goes over to the edge again. (01:05:40)
Continuity mistake: After the car falls on Batman, Grifter begins shooting at Black Manta. He is standing on top of a yellow car. When Black Manta begins shooting heat vision at him, the car turns green. (01:02:05)
Continuity mistake: While Batman is fighting Black Manta, he dives over as the bad guy blows a car into the air. The car is a light blue color and falls over on Batman. The next shot as Black Manta is walking towards it, the car has turned to a light orange color. Moments later when Batman crawls out of that car, it is back to being light blue. The car it lies on also changes from purple to orange. (01:02:00)
Continuity mistake: At the meteor crater in Metropolis, Flash and Batman are standing very close to the edge of the roof of a building. A few shots later, they are about twice as far from the edge. And then there is suddenly enough room for Cyborg to land between them and the edge, and Flash be able to take a few steps forward towards Cyborg. (00:46:15)
Continuity mistake: After Barry wakes up in bandages with third degree burns all over him, there is a spot of blood on his chest below his left shoulder. A good amount of the blood stain overlaps a line dividing two strands of the bandage. Moments later when he sits up, the blood is barely above that line at all. Later when Barry is sitting in the chair again, that same stain has completely changed shape. Other patches of blood on him also change. (00:36:20 - 00:38:00)
Continuity mistake: In the Batcave, Batman gets off a good punch to the side of Barry's head and knocks him over to a medical bed. There are two wine bottles on the floor next to the bed. A couple shots later when Batman is walking up to him, the beer bottles have vanished. (00:20:55)
Continuity mistake: Flash uses a speed boost of energy in his arm to fling the gray adhesive substance at Reverse Flash, slamming him into a glass display case and trapping him to it. The glass of the case breaks and cracks and the cracks around Reverse Flash's head are quite large. But after Batman makes his entrance and grabs Citizen Cold, that shot shows the cracks a lot smaller and shorter. They are back the way they were in following shots. (00:06:55)
Continuity mistake: Flash throws the explosive tops back at The Top who is standing on top of the headless statue. The arms of the statue are in a heroic pose with fists at his hips. The wrists are not bent. When the tops explode, the statue's right arm falls off. Moments later, Flash runs by this arm. The arm is now a left arm, as you can tell by the position of the hand to elbow and the thumb's placement, and suddenly the wrist is bent in a muscle flexing pose. (00:03:50)
Continuity mistake: When Flash zooms into the Flash Museum, he circles around a statue of himself and stops back in front of it. The statue's decapitated head is shown approximately 6 to 9 feet away from him, and there is only a little bit of debris around his feet. The shot cuts to some explosive tops landing at his feet and suddenly he is much closer to the statue's head, being now about 2 or 3 feet away from it, and there is much more debris around his feet. (00:03:25)
Continuity mistake: When Batman is interrogating Yo-Yo, he begins cracking her visor. The cracks disappear when Cyborg catches her. (00:16:45)
Continuity mistake: When The Flash first gets the liquid glue stuff over the villain, the bomb on it is about an inch away from the villain. In the shot where Batman lands on the ground after appearing, the bomb on the liquid glue thing is no longer there. (00:06:25 - 00:06:55)
Continuity mistake: When the Flash first runs into his museum, there are flames outside the door. When the scene cuts to inside, the flames are no longer there. (00:03:20)
Continuity mistake: Barry first enters his house to find it has been broken into, with the first few feet of the interior covered in glass. In the shot where he says "Mom" and the camera pans out a bit, the glass on the floor is no longer there. (00:01:40)
Continuity mistake: Just before Barry's mother notices the gas station, Barry is standing behind his mum on her left. Two shots later, Barry is suddenly standing behind his mother on her right. (00:00:50)
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)
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.