The Right Hand of God - October 24, 1974 - S1-E4
Revealing mistake: As Sam looks in the mirror, the trainer's reflection puts its right hand on Sam's right shoulder a split second before the camera view hand.
Genesis (1) - September 13, 1956 - S1-E1
Revealing mistake: Tom/Sam's wife and her reflection on the mirror do not match. The reflection moves her head, but the real person does not do that. (00:06:40)
The Color of Truth - August 8, 1955 - S1-E7
Factual error: The episode takes place in Alabama, however when Sam and the old lady are in the cemetery before Al shows up, there are mountains in the background.
Play It Again, Seymour - April 14, 1953 - S1-E9
Continuity mistake: The cut on Sam's face from the bullet is larger than the one on his counterpart's face.
Answer: Sam threw items off the raft to lighten the load, so it wouldn't sink, in doing so he made the raft less heavy. Which made easier to float with the currents, if it was heavy the raft would have moved slower and not moved so far.
Except that Al said that immediately after throwing stuff out of the boat four hours passed and it was shown that they didn't really move from where they were. They were still in the same spot. Forgot to ask this too. When Sam and Vanessa are stranded on the island, one of them, can't remember who, did something and when Al appears, he tells them that because of it, time had suddenly skipped several more hours and if the event hadn't been interrupted, they would have been rescued by a boat. So, what happened on the island that once again caused time to speed up? It seems kind of strange that time could move so quickly on the island, especially since it was still day time and it never showed any sort of changes like the sun or clouds moving.