Character mistake: In his opening prologue, Burt says the Graboids have been contained to the Northern Hemisphere, showing a map highlighting the Graboid attacks of the first film in Nevada and the second film in Mexico. However, it overlooks the Graboid/Shrieker attack in Argentina, in the Southern hemisphere, shown at the beginning of Tremors 3, an incursion Burt personally put down. It's not like it was classified - characters in that movie talk about it being reported by CNN, and characters in the Tremors TV series talk about it as well. And it's not like Tremors 3 is no longer canon, since Burt makes two references to being swallowed by the Graboid in that movie (which also becomes a plot point in Tremors 6).