When Quaid shows the new guy where to safely hold parts on the robot they are assembling, in the next shot the new guy doesn't seem to take any notice and puts his hand in the unsafe position again and continues working.
During the elevator scene, when Quaid and Melina are escaping, they jump down one level. When Lori enters the elevator area, they are on the same level again.
When Melina and Douglas hit the ground in the flying car she is injured, but between the different scenes her head is in different positions.
When Quaid walks down the stairs to the forgotten subway, a character is seen appearing behind him. In the next shot, the same character is seen appearing again.
While Melina is hanging from the elevator Hauser asks her for her gun but she still has it in her holster when entering the elevator.
For The Fall to travel the diameter of the Earth in 17 minutes, it would have to maintain an average speed of over 45000 kph (28000 mph). At this speed, it would be impossible for anyone to survive standing on the outside, because of both the airflow and the high temperatures resulting from friction.
If The Fall is free-falling and assuming no resistance, the occupants would be weightless for the entire trip. However people were shown in normal gravity except for the midpoint flip.
At 1-G the trip would take 42 minutes (a lot more than the 17 minutes as suggested in the movie), therefore the capsule has to be accelerating/decelerating at higher rates.
The music credits mention only Beethoven's Piano Sonata No. 17, but the first part Quaid played on the grand piano is actually from the first movement of Beethoven's Piano Sonata No. 14 "Moonlight" C# minor op. 27/2 - only the second piece is from the opening of the third movement of Ludwig van Beethoven's Piano Sonata No. 17 "Tempest" in D minor, Op. 31, No. 2.
In the memory dream sequence at the beginning, when Melina and Doug are shot in their hands, almost all you see is a red spot on her hand. A bullet has passed through both hands. Even with a small caliber, such a wound would cause continual bleeding, and this bleeding would be intensified by with the use of muscles for grabbing and supporting a person's body weight. Also, such a wound would make the hand almost completely unusable for weeks, perhaps even permanently, due to the pain and damage to muscles, blood vessels, ligaments, and tendons. Yet both of them continue to use these wounded hands to hold onto each other with no hesitation. If you want a comparison, try jabbing an ice pick through your hand, a far less destructive act, and then using that hand for anything.
When Douglas/Hauser is lead to Matthias, they go underground to take what should be the now forgotten subway. The action is supposed to take place in the future in London but the subway station and car look definitely New-Yorkish and absolutely not like any of the London Tube.
Assuming The Fall reached a terminal velocity, the gravity experienced by the passengers would slowly decrease to zero before reversing direction. The reversal would be barely if at all noticeable and so would not be the dramatic moment depicted in several scenes.
When the car crashes at the end of the car chase, you can see two buses. The 19 that travels between Battersea Bridge South Side and Finsbury Park and the 38 that travels between Hackney and Victoria. Neither bus goes near Parliament Square/Big Ben or ever has done. However, the film is set in the future...
At the very beginning of the movie, Melina falls down a shaft, she moves as if she is attached to cables and not free falling.
During the fight in their flat and the following pursuit Lori never reloads her revolver.
When Harry and Doug board the Fall, the announcement mentions that the time is 07:21 AM. Seconds later, when the Fall commences the descent, the departure time is shown as 01:35 hrs.
The Arabic characters written on the top left side of the passports are reversed , since Arabic is written from right to left , but when reading them from left to right they do make sense , they actually read "New Asia" which is the old name of the colony .
One hour into the movie Doug goes to check out a safety deposit box. After unlocking it, he carries it by the handle to a nearby table. Holding the box as so would cause all the contents of it would have fallen to one end. Yet when he lays it flat (horizontally) on the table & opens it, everything inside is neatly laid out & shows no signs of being tossed around.
When Quaid is opening his passport inside First Bank's vault, at the bottom of the page "Reed Henry" is mistakenly written "Reed Henty".
During the zero gravity scene the empty cases ejected from Quaid's weapon are clearly blank rounds. Furthermore, according to Newton's 3rd law of motion, the shooter should have move backwards whilst firing.
When Doug grabs Lori in a chokehold during their fight, he points a revolver at her neck. If he had shot, he would have successfully blown his own elbow off, assuming her neck wouldn't have stopped the bullet. This type of grab/aiming at the neck happens again later in the movie.
When Douglas Quaid (Colin Farrell) calls Bokeem Woodbine's (Harry) bluff when surrounded in the foyer of his residential building by shooting him in the head, multiple cops outside open fire with assault rifles into the foyer.
One officer in white was standing like literally right behind an officer in black and opening fire right into him! (1:06:46)
When Melina shows Douglas the scar on her palm the go to the back of her hand which doesn't have a scar. You would have one on each side with a bullet going through.
As Hauser plays the excerpt of Ludwig van Beethoven on the piano in his apartment to unlock The Key, his hands do not match the notes we hear.
When Doug and Lori are fighting, Doug gets kicked into a set of stairs. A crash pad is clearly visible when Doug hits the stairs and seconds later is not there anymore.
The "London Underground" train, is actually of north American design despite bearing London Transport logos and the station showing London Underground posters. This is because the scene was filmed in a Canadian Subway station. The train also looks very dated, there are far more modern 'futuristic' trains currently in use on the London Underground.
Assuming the Fall doesn't go around corners (which it patently could not based on its physics) then a trip from Australia (The Colony) would end up in the Azores, in the middle of the Atlantic Ocean. Conversely a trip from Britain would end up south east of New Zealand, toward Antarctica.
At the beginning of the film, it's stated that "The Fall" is the only means of transport between the UFB and the Colony. So the 'invasion' would be simple to stop, but just destroying the tunnel used by the fall, i.e. blow it up.
When Carl leaves the rebel base in the wastelands he is wearing a respirator, but he enters the "helicoper" without passing through an air lock. Thus he would be exposed to what ever the respirator was meant to protect him against.
Cohaagen would have told the most senior officer, Lori, to not kill Hauser from the outset. And why send in his most senior officer to do such a mundane job as nursemaid to Quaid in the first place?
Travelling through Earth (and its nucleus) just to save 40% distance, from roughly 20,000Km to 12500... doesn't seem to make much sense, nor would be that efficient.
On the TV news broadcast about 11-13 minutes in, the weather forecast is erroneously spelled "Weather FORCAST". This occurs in a couple of different scenes.