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.
Other mistake: At the very beginning when the scientists have uncovered a new chevron, it's the "Earth" chevron; a triangle with a circle on top, which indicates the planet of origin of the wormhole. However, ONLY earth should have an earth chevron - all other worlds have their own symbol.
Revealing mistake: When the village canon touches the hot poker to Teal'c's forehead tattoo, the profile view shows that the edge of the applique used by the makeup artist has separated from Chris Judge's face. It apparently was not glued down securely enough, and this is not an isolated incident. It happens quite frequently throughout the entire series.
Plot hole: When the team manage to create the cavern with the buried stargate they send Teal'c through to drill his way out, but wouldn't it be safer (and significantly faster) to fire a missile or two through and blast their way out? They have no idea how deep the stargate is buried, or under what type of rock, so sending Teal'c with only four hours of air seems suicidal.
Plot hole: In episode "The Nox," where we first encounter personal shields, Teal'c says he never saw that before (pointing out that it is a new invention). Yet when Daniel and Jack attack Seth, he activates one. Seth was trapped on Earth for thousands of years. How did he get hold of that?
Plot hole: When the team manage to cause the cavern to form over the buried stargate they send Teal'c through, but shouldn't the cavern be a vacuum? Air doesn't travel through the gate and the stuff caught in the vortex is destroyed, so Teal'c wouldn't need an oxygen mask he'd need a spacesuit.
Other mistake: In the last few minutes of this episode, Carter uses the DHD to dial home. She enters the first chevron, then the "Cannon" dies. And when she proceeds with the dialing,the first chevron is still encoded, and you can hear that she enters seven additional chevrons, which gives an equal of eight chevrons, and then engages the stargate. That would mean they are in another galaxy, referring to S02E15. In that episode they tried to dial the eight-chevron address from SGC but the computer wouldn't accept it. So, it is impossible that they would be in another galaxy.