Deliberate mistake: One of the bodyguard's rifle which is a Sig model SG553 only has a front sight and no rear sight. The rear sight can easily be attached to the Picatinny rail. Such a rifle is only good for up close instinctive shooting, anything at distance is spray and pray. (01:39:00)
Character mistake: Once Santino and Ares find John again in the hall of mirrors, John is fighting two of the grunt men that came in with Ares and kills them. Both of which had light assault rifles and weapons on them. John and Ares proceed to empty their pistols out at each other before she runs off with Santino. John then throws his empty pistol away and gets up to pursue his target unarmed and while limping. It is unreasonable to think that someone with his skill and training and experience would not take two seconds to reach down and pick up one of the guns dropped by the two men he just killed before chasing after his target, especially given the highly trained body guard with him accompanying his target. As well as probable encounters with more grunts. To add to this, he was seen doing just this moments before when he had limited ammo and each time he'd down a few enemies he would pick up one of their guns and continue. (01:41:30)
Continuity mistake: John shoots Santino once and gun slide locks open, showing gun as empty. In scene prior, John specifically checks gun and pats down Ruby Rose to get a fresh mag (and pockets a second) before heading to Continental.
Continuity mistake: While John talks with Winston at the park the sun changes between shots.
Continuity mistake: On the subway while John and Cassian eyeball each other, from the front there's no-one in front of Cassian, just a guy in a hat off to the side. But from the back, another man appears between them.
Suggested correction: You can see the edge of that guy cut off on the edge of the shot he is there, that grey hair and that same jacket.
Factual error: The party in honour of Gianna, Santino's sister, is held at the Terme di Caracalla (Baths of Caracalla). That site belongs to the city of Rome, and would never be used to host a private party, let alone a party in honour of a major Mob figure. Moreover, the place where John and Gianna meet while she's about to take a bath is the Horti Sallustiani (Gardens of Sallust), which are some 5 km away from the place where the concert is being held.
Continuity mistake: When John goes to his burned house for the last time, it is at night. It is still nighttime when the concierge comes to retrieve him to meet Winston. However, when he meets Winston, it is 5 pm, before sunset. Unless it takes 12 hours to get from NJ to Manhattan, the timing doesn't work.
Continuity mistake: The damage to the car after it gets smashed in the beginning the damage to the car is different to when he pulls into the driveway. (You can really notice when looking at the damage to the headlights in particular).
Continuity mistake: Before John starts to shoot Cassian by the fountain the blood on his left cheek increases and also the wound on that side gets smaller.
Continuity mistake: The amount of blood on John's right ab decreases when he is in the subway after the violin girl shot him.
