Arriving on planet Hanka, the billboard sign states it's PX8 987. The SGC team refers to the planet as P3X 987.
As O'Neill and Teal'c return to Earth to ensure that Cassandra is not sent through the gate, the decontamination sprays are not visible as the gate engages. Stock
footage of the unaltered gate room is used.
As Carter and Fraiser are applying CPR to Cassandra, her shirt is closed and opened between shots.
When Jack first looks at his watch during countdown to explosion, it says 7:42. The next time he looks at it, presumably seven seconds later, it says 7:41.
[at around 2 minutes] O'Neil orders the squad to "MOPP 4 everyone" (MOPP level 4), and they only don masks & hoods. MOPP level 4 requires mask & hood, protective over-garments, large rubber gloves, and rubber over-boots. There is no MOPP level consisting of only mask & hood.
During the thoracoscopy scene, Cassandra's SpO2 (percentage of hemoglobin bound to oxygen, as measured by pulse oximetry) repeatedly and significantly exceeds 100%. This is physiologically and technically impossible.
While Dr. Warner is using the scope to try and figure out what the object is inside Cassandra, her heartbeat changes drastically. When they cut to the heart monitor, every time it is set to "Adult" when Cassandra is 11 years old and would have a children's setting.
When examining Cassandra's blood work, Dr. Fraiser states that she has developed a severely low blood potassium level, which might explain her sudden onset of chest pain and arrhythmia. However, a look at her ECG rhythm strip during the thoracoscopy scene reveals strikingly tall, peaked T waves and a shortened Q-T interval, both of which would occur in the context of abnormally high blood potassium, not low.
Carter states that Cassandra has potassium metal in her body, which is very reactive. While true, the potassium would chemically react with the oxygen and water in her body to form potassium hydroxide and could not be present in a pure metallic form.
As the SG-1 team approach to tag the dead bodies on the world, just after the director credit disappears and Daniel Jackson finishes talking, the blonde-haired dead body appears to move its head.
When Jack is checking the countdown for the explosion his watch is set for time adjust that's what the TA top left means,
At the very end of the episode when Daniel Jackson goes to
sit down on the bench, you can see the transmitter to the microphone on his belt.
It is never explained how Teal'c is able to determine that the Goa'uld mothership - which has no identifying marks - belongs to Nirrti.
While operating on Cassandra Dr. Fraiser looks at the vital sign monitor and says her heart rate is 140. Yet the screen actually does not display Cassandra's pulse; the 140 on the screen represented Cassandra's systolic blood pressure, which was 140, and her diastolic pressure was 79.