Character mistake: At the end of the episode, after Lore has been defeated, Picard asks Data if he is O.K. Data replies, "I'm fine." One of the plot points of this episode is that Data cannot use contractions.
Character mistake: Captain Janeway states the temporal differential ratio is .4744 seconds per minute (meaning for every minute on the surface, only .4744 seconds pass on Voyager). Tuvok calculates that 30 minutes on Voyager would be 2 days 11 hours and 47 seconds. However, at that ratio, 30 minutes would be 2 days 15 hours 14 minutes and 15.9 seconds. Later Tom (who was on the surface) says the last two months for them was only 2 days for B'Elanna (who was on Voyager). But with the temporal differential, 2 months on the surface would be less than 12 hours on Voyager. 2 days on Voyager would be almost 253 days (almost 8.5 months) on the surface.
Character mistake: Tom Mason makes references to smaller armies defeating larger ones, of which history is rife with examples. He cites the Scottish defeating 'the British' at the Battle of Stirling Bridge. 'The British' did not exist at that time. The Scots administered a beating against the English in the Scottish War of Independence, against the Earl of Surrey, under Edward I. Someone with his level of knowledge would know that.
Character mistake: At the end of the episode, after Sarah has been tricked into revealing her plan and is rather obviously going to go to jail, Tru tells her that she "should have taken half," meaning that she should have settled for half of Andrew's money in a divorce instead of trying to get all of it by having him murdered. But Tru seems to be forgetting that Sarah has been trying to divorce Andrew all along, and it's Andrew who has stood in the way of that. Sarah would evidently have been perfectly happy with half, but Andrew prevented it from even being on the table for her, so Tru's comment doesn't make any sense.
Character mistake: The team are finding out who could have stolen the weather device from Madrona and find an energy spike at the same time SG2 are on a mission. "But SG2's mission is galaxies away from Madrona" Says Teal'c. At this time the only missions the teams could go on was in our own galaxy and couldn't be galaxies away.
Character mistake: In an early scene with Yvonne Hartman, she says "We've just measured the ghosts' energy at 5000 gigawatts." There are at least two mistakes here: (1) watts are a unit of power, not of energy (that would be joules); (2) later on, when Hartman is showing the Magnaclamp to the Doctor, she refers to imperial tons and says "Torchwood refuses to go metric", but a gigawatt is a metric unit.