Continuity errors/Stargate Universe

Stargate Universe

In every ending credits he appears, Darren Becker is credited as "Pvt" (Private). Yet, according to his combat fatigues he's wearing in "Air", Part 2, he is part of the US Air Force and should have the rank of "Airman".
In credits or in the dialogues, Hunter Riley is ranked as Sergeant. However, on his outfit, he's carrying Senior Airman insignas.