Factual error: The Pakistan Army uses British-style rank insignia with the crown replaced with The Star and crescent of Pakistan. The ISI officers are all wearing another badge instead of The Star and crescent. They are also wearing black gorget (collar) patches, whereas they should be wearing scarlet. Lt Col Khan and a number of other more junior officers should not be wearing gorget patches at all, as they are restricted to full colonels and above. ISI officers do not have a separate uniform; they wear ordinary military uniform if they are entitled to it.
Factual error: The man who approaches Carrie in the bar identifies himself as a 'lieutenant JG', and the pilot who bombed the wedding party in the farmhouse. However, it was F-15s that dropped the bombs on the farmhouse, making them US Air Force aircraft. The USAF rank structure doesn't include the 'JG' rank- that's a US Navy rank.
Continuity mistake: Carrie is holding her baby sitting on the couch. Left hand holding the baby, right hand holding the baby's left hand. Then it cuts to a different angle, Carrie's right hand is in the baby's lap and her left hand is on the baby's back. (00:32:50)
Continuity mistake: Carrie Matheson leaves her sister's house in a Jeep Compass with her daughter. When she arrives at her destination, she is in a newer model of the Jeep Compass (the front indicators are different).
Character mistake: Carrie tells Aayan that she can arrange for him to study at the Royal College of Physicians. The college isn't a medical school; it's a professional body.
Continuity mistake: Quinn is clean shaven when sitting by the pool with his girlfriend. The action shifts to Carrie in Pakistan and then back to DC where Dar confronts Quinn in the motel. Quinn now has a mustache and a bit of goatee, which he has for the balance of the episode. While the precise timeline is unclear, everything is fast paced and it seems that virtually no time has elapsed, certainly not enough time for Quinn to have grown a mustache.
Continuity mistake: As the young girl is in the kitchen cooking and goes to answer the door she puts her sari on. When she answers the door it's no longer on her head and is around her neck. When she closes the door she then has the sari back on. (00:05:10)
Other mistake: When Carrie leaves through the tunnel to the street, when she comes out of the store there's a shot of 2 people kinda looking at her. That shot was horizontally flipped - look at the sign on the door. (00:34:05)
Factual error: The Pakistan Air Force officer in the airport is listed in the credits as 'PAF Lieutenant' and is wearing the two pips of an army lieutenant. In fact, the PAF still uses RAF-style ranks, so he should be a Flying Officer, and the PAF also uses distinctive eight-pointed stars instead of pips.
Continuity mistake: When Lt Col Khan leans forward in the airport scene his epaulette can be seen to bear only the single pip of a second lieutenant. When he stands up again he is wearing the pip and emblem of a lieutenant-colonel once more.
Chosen answer: Everyone else calls him Brody or Sgt. Brody, and it probably became habit to her.
The_Iceman
Can't get the source but I read that even the Producer responded to that. Stating that it was common practise for a military wife living in a military complex as everybody refers to their husband by their last name.