After Dominika suffers a blow to her left eye, she enters Nate's apartment with a large gash surrounding her eye. As they hug each other and she gets ready to leave, her gash is completely gone.
One of her interrogators strikes Katya on the back of the head with a wooden truncheon. Such a strike carries an incredibly high risk of damaging vertebrae, or even detaching the brain stem causing immediate death. The risk of killing the subject of an interrogation through the use of such a strike, would be well understood by someone trained in interrogation technique. This is why rabbit punches are banned in contact sports.
Dominika suffers a broken left leg and has to use a cane to support herself. She is shown holding the cane with her left hand. This is not the correct way to support oneself if the left leg or foot is injured; she should use her right hand to hold the cane, thereby easing the pressure off the injured limb. Conversely, if her right leg or foot were injured, she should hold the cane using her left hand. When one walks, one's left hand and right foot swing forward, and then the right hand and left foot follow suit alternately. So, with her left leg injured, her right hand should hold the cane to help support the left leg.
When Dominika arrives at Heathrow Airport, it's stated that she is to board an Aeroflot Plane and there's an attendant wearing a red uniform. In reality, Aeroflot's uniforms are bright orange and nowhere close to the uniform shown in the movie.
When Nash is chasing Dominika to Heathrow with his van. The soundtrack is clearly a large to medium sized petrol engine with an automatic gearbox. Rather than the 1.6 or 2.0 Litre Diesel engine and manual gearbox that the Renault Traffic Van would have in the UK.
The floppy disks used by the agents may seem cumbersome and obsolete. However, in real life police and military still (as of 2018) use floppy disks to store classified documents. Since its impossible to hack or clone a floppy without having the physical disk in hand, and a floppy drive is needed to even read it, they are more secure than a smart phone or a USB memory stick, for example.
General Korlinoi's medals are US Army medals. They include the Silver Star, the Purple Heart and the Army Good Conduct Medal.
Lock Picking Technique. The Hook/Rake together with the Flat Bar Tension Wrench, are always required to be used, to actually pick a lock. By using the correct lock-picking tools, with the tension wrench in her left hand and the rake in her right hand, Dominika
Egorova unlocks Marta's locked room. Some people fail to see the rake in her hand when she turns around.
When Dominika meets Boucher in the bar, the bottle of Tanqueray 10 is filled with dark brown liquid.
But, Gin is transparent and has no color.
During the drive to Heathrow Airport, Colonel Volontov uses the sedan's rear-view mirror to converse with Dominika as if he is driving the vehicle.
At London's Heathrow Airport, there's an announcement about British European Airways over the PA system. That airline dissolved in 1974 when it merged with BOAC to become British Airways.
When Dominika arrives at Heathrow, it is stated she's entering Terminal 2, however both the interior and exterior shots are filmed at Terminal 5.
Boucher receives $250,000 in cash, but given current security practices, doesn't have a way to bring the money back into the U.S.
When Nate meets with his source, then is followed by Russian police, they shout "Stop! Militsiya!". Militsiya was the designation for the police force in Russia until 2011. The cars, however, have the word "politsiya" - Police in Cyrillic characters on the side, which is correct.
When the Russian interrogator leaves Dominika, as she picks up her pistol from the table she holds and carries it with her finger on the trigger. This is contrary to basic gun safety rules and it's unlikely that anyone with military or government firearms training would do this, even if the gun is empty.