Rene's grip on the champagne bottle changes between shots while pouring Mick's drink.
At the beginning of the final battle with the Anti-Monitor, he changes from facing right to facing left in between shots.
Lex Luthor accepts his Nobel Peace Prize at a small ceremony in National City. The Nobel Prize ceremonies are held in Oslo, Norway. However, this is intentional. This episode is set in a new universe; the purpose of the Nobel Prize scene is to be a sign that something is not quite right.
Clark did not realize that he has two sons rather than his son, Jonathon from Earth-38's reality, which is a plot hole as he is not a paragon so therefore should have known.
Sara claims that Oliver was the last person who knew her before she went on the Gambit and her life was upended. However, her mother is still alive (off-screen). She was last seen at Laurel's funeral and a death has never been mentioned by Laurel or Quentin.