Continuity mistake: Attempting to hitchhike, young Barry is running along the side of the road yelling at a car passing by. One shot shows his feet next to the road for several seconds with him not passing buy anything. The next shot is him running away from the camera, followed by a close up of his face as he runs. During this time, he never passes a vehicle or anything but open road to his left. Yet his mom suddenly reaches her hand out from off camera and grabs him, and the shot cuts to a wide angle and suddenly he and her are standing just a few feet away from their broken down car. Yet Barry was running along several yards of clear road and never passed anything. The car and his mother just appeared. (00:00:15)
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)
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)
Continuity mistake: After Young Barry's mom grabs him by the shirt, the camera angle shows their broken down car by the road. A few shots later as Barry takes off running towards the gas station, the distance between the road and the car has increased by about double. The patches of grass around the car also change around between shots. (00:00:55)
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: 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: 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: 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: When Flash goes around the decapitated statue of himself in the Flash museum, he stops and you can see a glass door behind him that is broken. The bottom-most part of the break is not to the bottom of the door frame, but a few inches to half a foot away. It then cuts to a view of his feet, and you see the same door behind him. Now the bottom part of the break in the glass is now right at the bottom of the door frame. (00:03:25)
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: 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: There is a large Flash symbol on the wall where Flash is trapped. The distance between this symbol and the ceiling changes a few times in the scene. It also changes position in relation to the display case Reverse Flash is trapped against several times in the scene. (00:04:25)
Continuity mistake: After freeing himself from the wall where he was pinned with boomerangs, Flash takes off as Captain Boomerang and Captain Cold continue to attack him. Cold shoots ice on at him that gets on the wall. A few moments later when Flash hits that wall again after his foot is frozen, the ice that Cold put on the wall moments before has vanished. (00:04:30)
Continuity mistake: The Flash gets his foot frozen in the museum fight scene. The ice on his foot disappears in the shot after The Flash says "The gang's all here". (00:04:50)
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: Reverse Flash places a bomb on the gray adhesive substance that he has trapped Flash in next to Flash's head. From the side angle in that shot, it shows it right above his shoulder. But a couple shots later when Flash begins vibrating his arm at super speeds, the bomb is suddenly much further to the right, away from his head. (00:06:15)
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: 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)
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: As Superman is escorting Reverse Flash down the steps of the museum, you can see the top part of Reverse Flash's red lighting symbol over lying the black circle and extending up into the yellow of his suit a few inches. It then cuts to a different angle and the tip of it is barely a few millimeters above the black circle. Also between shots, the bottom yellow triangle part below the S on Superman's chest suddenly gets much larger. (00:11:10)
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.