Factual error: Many times the Captain is wearing a red baseball style cap. This is only worn by the Captain when drill is underway to signify, "I'm here, but not really here for the purpose of the exercise."
Factual error: Throughout the combat sequences with the Russian submarine, both the enemy sub and the missiles exchanged between the USS Alabama and the Russian sub are shown as blips on a radar scope. In real life, sonar displays look much different and resemble a "waterfall" pattern that trained sonar specialists can read.
Continuity mistake: In the scene where the "Alabama" dives, what we see isn't a ballistic missile-carrying submarine (SSBN), but an attack sub (SSN); actually more than just one, since the masts and periscopes keep going up and down in different shots. It seems that the navy wasn't too willing to cooperate in the production of a film depicting a mutiny onboard a nuclear sub, so the shots were "stolen" from a helicopter in the vicinity of some navy base.
Chosen answer: The ship has a second antenna, but the radio is damaged during the torpedo attack. Therefore they have to fix it in order to use the backup antenna.