Other mistake: Carter says that the chance of depositing the heavy element inside the Katow sun while the element is en route is about 1%. However, hypothetically speaking, the actual chances would be infinitely smaller, in fact it would be near impossible. Simply consider the distance from earth stargate to the Katow stargate, the diameter of an average sun, and the time it takes for an object to travel through the gate (about 12 seconds). Taking the closest star to us (Alpha Centruri), at a distance of 4 light years, this means that the wormhole takes ~443ns (0.000000443s) to pass through the sun (using our sun diameter). Similarly, taking the diameter of the Milky Way as the distance to the furthest star in our galaxy, ~100000 light years, meaning the wormhole takes ~17ps (0.000000000017s) to pass through the sun. This means that the SGC would have to shut down the gate within a a maxmium of 443ns or a minimum of 17ps time gap. As we have previously seen, the stargate takes far longer to shutdown than these miniscule time lengths.
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).
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.
Factual error: In the scene where O'Neill and Maybourne are looking up NID flight plans, the plan viewed on the computer lists the destination airport as Minot Airport Base, but provides the airport code for McCarran International Airport (KLAS). It also lists non-existent runways, as in runway headings that do not exist anywhere in the world. (00:24:15)