Continuity mistake: After Moco and Azul finish their telephone conversation about how many of Moco's men Azul killed, Azul leaves, but one of Azul's men goes back to see Azul's women. In the background, there are posters of the Playboy bunny logo and a woman on a jetski. Ashe runs away from the lethal women, the posters are nowhere to be found next to the doorway.
Revealing mistake: When Azul is in the bar and goes into the men's room to execute the man inside, we look straight at the men's room door. You hear a gun shot, but you can see you can see a flash reflected. That means that what ever made the gunshot sound was behind the camera. Also in the same shot you can see a man's shadow on the door.
Continuity mistake: When the mariachi is being chased, after they've left the hotel, he runs up a truck and two of the bad guys shoot each other trying to hit him. He picks up a gun to shoot at the other bad guy. The gun he actually fires is a completely different type of gun. When he drops it, it's changed back to the one he picked up.
Continuity mistake: When Azul is in the bar, just after killing the men at the table and the barkeeper he puts his machine gun back in his case leaning against one side and picks up a sawn-off shot gun. When he comes back from the toilet, the gun is back in the case and not visible anymore.