Plot hole: The team go through the gate to disable a drone with the intention of being able to close the active Stargate, but once they go through in a submarine, the gate closes behind them, rendering the mission pointless. (00:24:18)
Suggested correction: This entry seems to have been made without watching the episode or you skipped a part. When the 3 enter the Stargate via the submarine, the Gate does NOT close behind them. It stays open, which we not only see but is how they can communicate with O'Neill. Then Dr. Markov says once they bring the drone in (to the submarine), they can shut the drone off and the Gate will close. Which is what they do (off-screen) and when they do, the Gate closes.
Plot hole: Despite the Russian Government not being aware that the submarine is quarantined in a US port, a Russian Navy Sovremenny-class destroyer is visible in the background. (00:14:29)