At approximately 15 minutes in while Sheriff Longmire is meeting with Officer Mathias at the Red Pony a close-up of Mathias' name tag shows it misspelled as "MATHAIS." Later, when the Sheriff and Mathias are outdoors discussing the Mexican cartel at the approximately 24 minute point, Mathias' name tag is correctly spelled as "MATHIAS."
From 27:07 -Music can be heard playing but as soon as Walt yells: "sheriff's department" the radio is magically turned off.
When Vic is checking the room keys at the hotel, the door she tries right before the final door scans green like it accepted the card.
At the hotel before Vic and Longmire open the door, Longmire draws his gun twice. First after he motions the manager out of the way, and then again just before Vic opens the door.
At 14:24 - Officer Mathias' name tag has his name misspelled as "Mathais"
Sheriff Longmire states that the magazines they found at the hide are for an AK-47, but in reality the magazines can fit the AK-47, AK-74, the AK-12 and many other variants. All of these weapons are variously manufactured as semiautomatic or full automatic rifles.
From 00:57 to 01:06 -The rope used by crew members to help Walt can be seen.
At 39:37 -"blood" on the camera lens.
When Walt is approaching the trailer, someone pumps a shotgun behind him. When he turns around, the man is holding a double barreled shotgun, not a pump.
When Branch is questioning the gang boys, he asks if they've heard of "El Lupo." One of the boys says "that's Spanish," and Branch replies, "actually, it's Italian." Actually, it's neither and it's both - the writers used the Spanish article "el" and the Italian word "lupo." To make it one or the other it should have been either "el lobo" or "il lupo."