Other mistake: Preacher has a large bold tattoo at the center of his chest below his neck that changes repeatedly. For example, it's dark and clear when they capture the deputy, but it's smudged and partially gone when Preacher forces Stella, the deputy, and Ralph into the 18-wheeler. (00:29:10 - 00:36:50)
Other mistake: The instructions for the "manual improbability button" are written in English on an alien spaceship.