When Bart is waiting for the approaching subway train, a shot of the back of his head clearly shows his self-inflicted gunshot wound. A few minutes later, when he gets up out of his seat on the subway, the back of his head shows no wound at all.
When Joey is being held up by the Hispanic thug, the chrome metal part of the carjack he is holding slides out. The following scene goes to Bart standing up, then goes back to Joey, the carjack is together again. Then the next scene when Joey goes to hit the thug in the head, it is missing the metal half again.
After Bart comes back from the dead, his body clearly shows the incisions and sutures from an autopsy. With battle deaths and other cases in which the cause of death is obvious and undisputed, autopsies are not necessary nor performed.
When the Vigilante Gunslingers bust the corrupt cops in the warehouse, there are some close-up shots of their faces, wearing sunglasses. Through the glasses, it is visible that both actors aren't wearing the zombie contact lenses at that moment.