At 14m 27s - Miguel is shown Johnny's photo where he is "wearing a shirt". The name "Billy Zabka" can be made out in the top left corner, clearly indicating it may have been a magazine or modeling photograph.
During the second Vietnam flashback, when the Sergeant is about to hand over the red envelope to the captain, he passes it from his right to his left hand and reaches towards the captain with his left. But then the angle of the shot is reversed and he is handing it over with his right hand.
When Armand Zakarian is having dinner at the LaRussos', the food he is holding switches between his right and left hand between shots, and at one point he is suddenly holding a fork, which he wasn't in the previous shot.
Kreese's friend has hair gathered into a bun. Man-buns would not have been allowed in the Army.
Daniel says that he brought back soy sauce with a Kit-Kat flavor from overseas. But that doesn't make sense at all. Soy sauce isn't a brand name, it's just a condiment, so grammatically it's wrong. Literally he's saying soy sauce that tastes like a Kit-Kat. No where do they make such a thing. It would just be chocolate sauce. What he most likely means is that Kit-Kat has a soy sauce flavor. Which is true, that product is real.
The actor portraying the spec Ops CPT is too old for the rank.
After Johnny eats the sushi roll, Miguel is scrolling right through his photos. Since the sushi photo was the most recent taken, it should've been the first photo seen, not the third.
At 0:40min, the soldier in the Vietnam 1968 flashback, sniffing Creese's mail from his girl back home, has an obvious ponytail tucked in the back. The US army would never have allowed that.