During the opening chase sequence, Eggsy is wearing a midnight blue suit and his attacker is wearing a lighter blue hooded sweatshirt. Eggsy is shown on the floor of the car almost falling out the door and his attacker is on top. When the film moves to a distant shot, a stunts person wearing a light blue shirt is on the bottom and another stunts person wearing a dark blue shirt is on top. This scene is out of order and would work with the previous fight close up when the characters are reversed.
When Eggsy is having dinner with Tilde and her parents, the King of Sweden explains to Eggsy that he should be addressed as "Your Majesty." Living in a monarchy, Eggsy should have known this already, particularly after his Kingsman training, which included a significant etiquette portion.
While toasting fallen comrades, Merlin and Eggsy nearly finish the bottle of fine spirits. The level of liquid has fallen well below the label. In a longer shot, the level of liquid has risen up to the label.
During a scene at Statesman's Kentucky distillery, Champagne (Jeff Bridges) takes an unwrapped cigar out of a tube and smells it. A short time later, when he asks Tequila if he is feeling alright, he points at him with the cigar that now has a plastic wrapper on it.
While descending on out of control the ski lift, the high speed spinning of the lift would have caused it to act as a gyroscope. Rather than swinging back and forth like it was it would have stayed in a fixed position.
The tracking device that Eggsy plants on Clara is said to be absorbed by a mucous membrane. Eggsy is forced to resort to sexual contact for this. But there are mucous membranes in the mouth and stomach as well. Simply putting the tracker into something she would eat or drink would have done the trick.
When out of control ski lift sequence starts, on exterior shots it is the right cabin where the sequence happens on the right track ropes, rolling on high speed when it passes over the first supporting tower from the right side. In the next exterior shots when track and hauling cables snap and onward it is the left cabin on the left track ropes on the left side of the supporting towers.
After Whiskey put his bullwhip around Galahad Sr.'s neck in the diner, he took several steps toward Galahad Sr., but the bullwhip neither sagged lower nor retracted into the handle in came out of. This means it was clearly 100% CGI, and they just forgot to compensate for the movement.
When Merlin is using the mine sweeper bat as they go thru the jungle towards Poppy's place, Eggsy steps on a mine trigger.
After Merlin hands the sweeper to Harry, he freezes the trigger and replaces Eggsy's foot with his own.
Then as Harry and Eggsy proceed thru the jungle, neither has the mine sweeper nor seem concerned one bit about further mines.
Harry's left eye was shot and he was given a pair of glasses with the left side darkened. But at Eggsy's wedding, Harry's glasses appear to have the right side darkened. This is because the scene shows Harry and Eggsy reflected in a mirror.
Eggsy tells Harry that he knows that Kingsman agents shouldn't be in relationships, but in the first Kingsman movie, Harry teaches Eggsy in his home office that a Kingsman's name should only be in the paper 3 times: when they are born, when they get married, and when they die. Also, Eggsy's dad was married to his mom at his time of training. Why would he have been recruited if agents aren't allowed relationships?
Charlie's new metal arm is so strong he can throw a bowling ball through a concrete wall, but when he slams Eggsy into the ground with the same arm, Eggsy is unharmed. The minimum damage would be a broken spine.
Given all of the technologies that Kingsman has, all failed recruits (such as Charlie) should have their memory cleared with the amnesia needle for their own security concern. It is questionable why a top secret agent like Kingsman doesn't have concern about this. However, this means Eggsy has to get amnesia too, which cause a plot changes.
The Statesmen flood Harry's room in an attempt to undo his amnesia and give him the shock that will bring his memories back. But when the water drains, the things on his desk are completely undisturbed.