The Men That Corrupted Hadleyburg - S2-E18
Audio problem: Final sound edits were incomplete on this episode when star Pete Duel committed suicide, so his dialogue is "looped" by another actor in several places. Though it's an excellent imitation, it is most noticeably not Duel's voice when Heyes and Curry are waiting for Harry in the opening scene, at the campfire with the Tapscotts, and when Harry tells them about the trial's outcome.
The Man They Called a Magician - S1-E2
Audio problem: Jigen shoots Pycal in the head with no results. He says that his gun is useless, but his lips don't move. (00:05:50)