Unnatural Selection (2) - S6-E12
Other mistake: When Thor reveals to SG-1 that the Replicators have reversed the time dilation device, he says time is moving at a factor of "10 squared" (100 times faster than real time). Carter says that in the hour that passed, 4 days have passed for the Replicators (which is correct), but then says depending on when they did it, hundreds of years could have passed. But that's not possible since that means years in real time would have passed. But the Asgard didn't set this trap years ago, just recently.
Summit (1) - S5-E15
Plot hole: During the briefing at the Tok'ra base about the deadly symbiotic poison, Ren'al says that dying symbiotes release their own toxin which is just as deadly to the hosts. Yet in other episodes when a symbiote dies in the host's body, the host doesn't die, even without medical treatment. For example, the whole infected town of Steveston is just fine when all the symbiotes are killed (s06e05).
Other mistake: In several episodes throughout the series, SG-1 is coming through a planet's Stargate but there's no sign of a MALP, even when it should be in the shot. SGC wouldn't send a team through without sending a MALP first (not only to check for a DHD, but survey the land, check for habitability, etc). And if the idea is "well, maybe they have a recovery unit go fetch it before SG-1 goes through", then why would the MALP be present in all the other episodes?
Brief Candle - S1-E9
Other mistake: Jack made it quite clear that he was 40 years old when talking to Kynthia, so if his birthday was in '52, that would put him at 45, instead of 40 years old.
Factual error: In several episodes, there are mentions of travelling many million light years, even though they're still in our own galaxy. However, the Milky Way is estimated to be around 100,000 light years in diameter.
Character mistake: In newspaper article "Anubis plans to retake Dakara", there's a line that reads "being partially ascended has it's benefits." The word should be "its."
Character mistake: When Daniel Jackson learns about the fact that his wife, Sha're, has returned with a dormant Gua'uld, he does not take her to Thor's Hammer that got repaired in S2E6. Even though he was with Teal'c, that doesn't pose any issues since he is deliberately exempted from the Hammer.
Visible crew/equipment: At the very start in the briefing room, the Trinium is being passed to Sam and Jack as the camera tracks left, and we can see the reflections of standing crew (Daniel, Sam, and Jack are seated) and the moving boom mic on the glass window, towards the left. (00:00:15)
Visible crew/equipment: After Jack kills Fro'tak and disintegrates his body with the Zat gun he hides from the guards, then as soon as it cuts to Teal'c and Drey'auc at the house, four T-marks become visible on the floor - white, orange, pink, and blue. (00:23:15)
Visible crew/equipment: After Daniel finally collapses in the supply room Jack hugs and comforts him, then it cuts to Sam telling Hammond about the probe's data, and an actor's T-mark is visible on the floor near the stairs. (00:39:10)
Visible crew/equipment: When Teal'c is being led away in chains Hammond says the chains were Maybourne's idea, and as the camera is dollying out the chalk T-mark becomes visible on the floor at Jack's feet, particularly when he walks away. (00:11:00)
Visible crew/equipment: After Simian has revealed to Hammond and everyone else why Linea is known as the Destroyer of Worlds, the alarm soon blares and Hammond races to the Operations room. When he's told about the unauthorized gate activation, the white T-mark is visible on the floor. (00:41:00)
Character mistake: At the end, Vala and Mitchell establish a wormhole and let Teal'c and Jackson know. Almost a minute passes before Teal'c and Jackson get back to the gate and Jackson yells "run" because they need to get through the gate right away. Obviously they're detained, but after being let go, Mitchell says they're sending the iris code now. This is something that should have been done sooner, especially after hearing gunfire, so they could be ready to go through when Teal'c and Jackson arrived.
Suggested correction: OR... after hearing the gunfire maybe it was smarter to wait until they verified that it was Teal'c and Jackson who prevailed. Otherwise, they risked leaving the gate open to a hostile force.
Perhaps they waited, but they still would have sent it when they saw them, which the didn't. And they've never waited like that before.
Plot hole: And the end, when Vala and Mitchell activate the Stargate home, SG-1 is delayed in being able to step through because they are detained. However, the whole time they're detained by the gate, there's no radio transmission from SGC. Later we find out they're coming home early, so on SGC's side, they just had an unscheduled off world activation and would know it's from the planet SG-1 is on, and they would radio for an update. None of that was done so the conversation could happen.
Continuity mistake: When SG-1 is tied up, Carter has blood going down her cheek and from her mouth right before being beamed up. In the next shot on board, the blood is gone.
Continuity mistake: The way the C-4 is placed on the blast door changes in various shots.
Continuity mistake: When Hoskin is shot by Carter, the position of his body changes from how we see him to land to the next shot of him when Carter approaches him. At first his arm is extended and his coat lands to cover his gun. In the next shot his ark is by his side and the coat is tucked under but you don't see his gun.
The Warrior - S5-E18
Continuity mistake: When Teal'c and K'tano are fighting and K'tano says "is that the best you can do", you see Teal'c's training staff on the ground and it's already broken, even though that hasn't happened yet. When Teal'c stands up, that's when K'tano breaks his staff.
Other mistake: In a Russian facility in the kitchen no-smoking sign instead of "не курить" reads "не курять", which is gibberish. (00:26:07)
Continuity mistake: When Omoc is approached in the infirmary, he takes off the oxygen mask. But in some shots, the mask is just pulled down and still around his neck.