A grenade is thrown and lands inches away from kegs of powder and a few feet away from a knocked out Tony. Doug comes to the rescue, but the grenade is now behind Tony when it should be next to the powder kegs.
When the aliens are taking Doug and Tony to the cave. Tony says "It's a force field". Just to the right of Tony's shoulder you can see tire tracks. This was set in 1883, tires hadn't been invented. But a moment later the tire tracks disappear.
In the fight sequence at the end, Tony is pushed into one of the boulders inside the aliens' lair and it moves, revealing that it is made of some very light substance.
When Doug and Captain Henderson are breaking into the alien base, Doug pours a trail of gunpowder as a fuse to a keg of powder. But when he lights it, it is obviously a trail of liquid laid in a small trench.
Tony and Doug arrive in the Sudan in the midst of the Siege of Khartoum on November 2, 1883. However, the siege lasted from March 13, 1884 to January 26, 1885.
Captain Henderson should be wearing two pips on his collar instead of three. The rank insignia he's wearing didn't go into effect until 1902.
Dr. Swain gives the position of Tony and Doug as 16° South latitude. But Khartoum is at 16° North.
The alien leader (Kevin Hagen) has a human lower face whereas the other aliens have whole insect-looking herds.