Character mistake: When Wes is drinking the mezcal with the worm in it, he makes a toast to "la vida luna" and tells Sissy it's Spanish for "the crazy life". This is untrue, the correct Spanish translation for "the crazy life" is "la vida loca". "La vida luna" literally translates as "the life moon" or better yet "the moon life", but a more accurate translation is "the night life."
Continuity mistake: The movie is supposed to have been filmed and taken place exclusively in Pasadena, TX, and MOST of it is. The trailer park that they live in, however, is NOT in Pasadena, or anywhere near there. There are several scenes where they show someone driving into the trailer park, and you can see mountains in the background. There aren't any mountains within hundreds of miles of Pasadena.
Continuity mistake: When Bud and Sissy are driving to their new home, the camera shows their names on small license plates in the rear window of the truck. They arrive at the house, and you can see a bunch of people and streamers in the back of the truck. They were not there when the license plates were shown.
Revealing mistake: When Bud and Wes take competitive turns riding the bull at the presumed high speeds, the bucking patterns and timing aren't consistent. A few times either man goes less than 15 seconds on a mid speed rather than full on bucking. Which even for a practice doesn't add up, and wouldn't fly during a competition.
Plot hole: When the mechanical bull ride first opens up, riders need to pay $2 per ride and sign a waiver that if they get hurt, the bar is not responsible. But later in the film, riders (especially Bud) now just jump on and take a ride without paying (or signing but even if only needing to sign once, the money part is still in question here). How is it suddenly free?