Goodbye, Farewell, and Amen - S11-E16
Deliberate mistake: BJ mentions to Charles that if they don't sign the armistice it will be the second time in 2 years and then he will miss his daughter Erin's second birthday. This is BJs 7th season and when he arrived at the beginning of season 4, Erin was already born, making it absurd that seven years later she could still be one year old. Because the real war lasted 3 years and the show 11, there are obviously some errors like this that can't be avoided but this was blatantly egregious.