Other mistake: Season 8, Episodes 16 & 17 - "Reckoning" The Replicator ship on which Daniel is being held prisoner is supposedly made entirely of Replicator blocks (a fact established in earlier episodes), yet only the walls of the set are made to look that way. The floor, visible repeatedly throughout the episode, is simply a concrete slab painted the same gray color as the block walls.
Plot hole: Huge plot error: Apophis and Clorell (Skara) should not have survived the explosion in Season 2, Episode 1 (when they attack Earth with two ships). In "Family" they explain that Apophis and Clorell survived by escaping through the stargate aboard Clorell's ship moments after Daniel Jackson did the same. However, when Daniel Jackson escapes through it, Apophis and Clorell are not even on the right ship, and there is 1 second left on the C4 timer when Daniel escapes. They actually show Daniel Jackson escape, and then cut to Apophis and Clorell still aboard their ship. So apparently, Apophis was able to "ring" from his ship over to Clorell's ship, make it to the stargate room, dial an address, and escape through the stargate all within literally 1 second. Is this guy related to The Flash?
Continuity mistake: Daniel's interaction is inconsistent across the episode. Initially, Daniel emerges through the Stargate with no ripples in the event horizon or audible noise. Then he walks down the metal ramp making noise with each footfall. Later in the episode he returns through the Stargate with an audible noise and ripples in the event horizon. He remained "out of phase" for the entire segment of the episode.
Factual error: The escort for Colonel O'Neill is wearing both Major and Staff Sergeant rank insignia. Probably what the writers thought was a "Sergeant Major", which does not exist in the Air Force. Major is a commissioned officer, sergeants are non-commissioned officers.
Continuity mistake: When Daniel returns to the SGU in the alternate reality and Cathrine shows him the map of where the Goa'uld attacks on Earth are, we can see that there are no attacks in the north of Europe, but when we see a closeup Oslo, Stockholm and Helsinki have suddenly been added.