While the men are in the truck talking, a sandwich being eaten has the bite area alternately changing from one side of the bread between shots.
At the end of the truck ride to Vegas, Hughes doesn't know how to open the passenger door from the inside, but in Dummar's flashback at the end of the movie (when Hughes gets to drive the truck), Hughes has no trouble opening the door.
When Melvin and Howard are driving the pickup truck into Vegas during the movie opening the drivers side headlight is out. When Howard is driving the truck during the closing both headlights are operating.
The scene where Melvin and Linda are gambling in the casino, their young daughter is sitting with them. Minors are strictly forbidden in any casino gaming areas, especially next to the tables.