When the "Ferrari" is speeding to the rescue through the dark streets of Miami, some cuts show it with a single tail light while most have both lights working. The same shots are used in several episodes.
When Ludovici Armstrong is confronted by Nicky the chauffeur, he raises his hands -- and the shotgun he is holding -- in a gesture of surrender. In a subsequent closeup of Ludovici, we see him raise his hands again.
When Linus Oliver is being tailed by OCB, we see his limo driving down the street. Trudy then complains that Linus has made a U-turn to shake his pursuers, but when we see his car again, it is still driving in the same direction down the same street (the same construction equipment is visible in the background in both shots).
The shot made from the tower in the manner shown (standing freehand) would be impossible for even a skilled shooter. A shot of that distance would require the use of a rest. Further, the crosshairs in the scope do not reach the center, so it would be difficult to judge where the bullet will hit.
When Ludovici shoots Nicky, the wiring for the squibs that simulate the bullet impacts can clearly seen coming from the bottom of Nicky's pants leg.
In the shoot out in Crockett's, Crockett is standing behind an inside wall. At that range with that weapon, the dry wall would not have stopped the rounds. Crockett would have been cut down.
When Tubbs points out Calderone to Trudy in the FBI surveillance photo Zito hands him, he points to the wrong man. Calderone is actually to the left of the man Tubbs identifies.