When Marcus and Sinclair stop to watch the T-Rex, close-up shots of them in the cab show a red truck outside the shotgun window. In longer shots there are no vehicles at all parked near them.
Almost all bullets have copper jackets and lead tips, neither of which make sparks, so bullets do not make sparks when they hit metal objects. Shooting a propane tank would not ignite the gas inside, therefore it would not explode.
Many times throughout the film people are seeing firing guns without cycling the action. Most notably during the final battle at the mine, Sky fires her pump action shotgun repeatedly without cycling the action, and Quaid is seen firing an M-60 yet the belted rounds clearly are not advancing through the action, nor are any spent shells ejected.
When Sky calls the sheriff from the diner, the phone she uses plainly has no communication chord connecting it to any phone jack outlet.
license plates of several of the vehicles read 7p (Flathead county), the "hero's" plate changed from 2 different plates to a 7P county as well. but for Flathead county, trucks would have a 7T not a 7P.
While biologists have theorized that it could be possible for life-forms to develop in a methane based atmosphere, there is no way an organism that developed breathing a oxygen/nitrogen based atmosphere could adapt fast enough to a high methane environment to survive. And assuming that it were somehow even possible, had the dinosaurs trapped underground adapted to breathing methane, once they escaped the caverns and were exposed to our oxygen/nitrogen atmosphere they would asphyxiate to death.
In the beginning of the film, one of the armed security guards is carrying an AR-15 rifle, yet has shotgun shells on his vest.