Plot hole: The car was tracked down by finding the original car key on Jimmy's body. If he had stolen the car from the original owner, how did he come to have the original car key?
Episode #1.3 - S1-E3
Plot hole: The killer is meant to create the perfect crime, but the angle of the shot would make obvious to any forensics examiner that it's a suicide. There is practically no possibility for a person supposedly positioned across a long dining table to kill someone else with a shot under the chin. (00:55:50)
Episode #1.2 - S1-E2
Plot hole: Contrary to any other version (including the novel), here the mastermind behind the murder realises in timely fashion that burning the letter was a mistake, it was not actually part of the plan. With this change, they'd have still all the time in the world to go back to the compartment and get the burnt remains, but they simply do not.