In the showdown scene in the women's bathroom, the two characters switch positions in the mirror shot, most likely to create uncertainty in the viewer. Note the color of the sleeves at the shoulder (creme vs blue). To make matters worse, the style of the earrings also switched between both characters in the mirror shot.
If it was 2073 (as shown on the stage of the gala) and the CAB was introduced 30 years prior, then it was 2043 during the events in the beginning of the movie. The iconic quote then states that "in 50 years we have doubled our population", but in 1993 population was already over 5 billion, so it should have been more than 10 billion in 2043. However, in the next line it says that population is only estimated to reach 10 billion by the end of the decade - which would mean 2049/2050 and thus contradict the previous statement.
When the agents have Wednesday Karen cornered in the bathroom, for one moment the green ID light is not lit on one of the agent's guns.
The microwave oven exploded exactly when the countdown timer reached 00:00. However the timer is not a detonator, it does not turn on anything. The end of the interval is the moment of switching _off_ any power. Any destruction can occur _before_ 00:00 only.
When Dafoe's character is teaching math, he got the transformations of the equations on the whiteboard wrong. The second line does not follow from the first one.
Two of the sisters are missing, but Friday identifies the eye in the bag as Tuesday's. Identical twins have identical DNA, meaning there should be no way to tell whether the eye belonged to Monday or Tuesday.
When the clock hits midnight, and the sisters are at the table wondering where Monday is, the sister leaning against the chair has all ten fingers. When the camera zooms slowly out, you can clearly see the left pointer finger disappear mid-shot. This only looked like a goof due to the position of the fingers and the lighting. At no time during this scene is she shown with ten full fingers.
When the two sisters are giving directions to the sister who is fleeing from the bureau agents: Just as she leaves the factory building, she is told to go to the left, but she actually goes to the right.
However, she is told "Next left, there is a door at the end of the alley" but as she is already at a junction, "Next" implies "not this one, the next one", which she has to turn right to reach.
After the explosion which engulfs in flames and blows a group of CAB officers across a corridor, the main guy shows up very soon after without a mark on him, and his shirt and tie have no effects of the event.
In a scene with Adrian and Saturday there is a camera shot behind Saturday where you can see dark brown spiky hair underneath her smooth wavy blonde hair.
Although the whole movie was shot in Romania, at the 1:22:47 mark a Turkish male (probably an assistant) shouting "Arkada kaldin, arkada! Gel buraya!" could be heard. This can be translated as "You stayed behind, (stayed) behind! Come here!" into English.
The septuplets' grandfather (Wilhem Dafoe) had raised them since birth, so it's uncleared why they all foster the Swedish accent that Noomi Rapace sports instead of an American accent like they're supposed to. There is no logical way they all could have possibly developed an accent they were not privy to from birth. It would have been less noticeable had the grandfather that was cast also had an accent, or Wilhem Dafoe made some attempt at an accent.
The same CAB infomercial is shown during the introduction and is played later on the public screens, although 30 years have passed since the one child policy was announced.
While it is clearly shown that Tuesday's left eye was removed by the soldiers earlier, Tuesday is seen later near the end with a functioning eye.