Revealing mistake: When Al is running from the fire in the incineration chamber, fire is shooting out the back. When the fire goes away lights can still be seen in the chamber entrance. The fire should have incinerated them, because this area would be sealed off from the hot area during normal operation.
Revealing mistake: When Dirk and Al are struggling through the desert, chained to the trailer, they slip and fall into the pit. They coast down the slope, thud into a drift and fly through the air and land. However, in the next scene, their tracks are shown behind them as if they had not flown through the air at all.