Factual error: After Linnet Ridgeway had almost been crushed by a stone falling down from the temple of Karnak, Dr. Bessner advised her to go back to the boat to have a rest. She replied that it can be for just a couple of hours, as she must see the temple of Abu Simbel in the evening. In the next scene, she is really visiting Abu Simbel together with Simon and in the late evening they are back on the Nile steamer. This is absolutely impossible, as the distance between the temple of Karnak and the temple of Abu Simbel is about 400km (250 miles). By that time, it would have been impossible to manage 800km (500 miles) within one afternoon just for a visiting tour. And it is not very logical, as the Nile steamer was going up the Nile to Wadi Halfa, so they would have passed Abu Simbel anyway later during their trip.
Factual error: In the Abu Simbel scene, watch closely when they show a side-view shot of Jackie, accidentally depicting the shores of Lake Nasser in the background. This reservoir was built only in the 1960s and didn't exist at the time the movie is set in (1930s). (In fact, the whole temple had to be cut from the rock and moved to higher ground following the completion of the Aswan Dam, so the "original location" was no more available for the film crew.)
Factual error: The body of Louise (the maid) is discovered when the room-service guy drops a towel on the floor and it lands in a pool of blood. The blood obviously ran out of her cabin from under the closed door. However, the cabin door thresholds are not at level with the floor (neither outside nor inside the cabins), but several inch higher, so her blood could not possibly have escaped through the cabin door. All along the movie you can see the actors carefully stepping over those irritating thresholds in order not to stumble, though I think it is hard to spot the edge from within Louise's cabin. But watch when Dr Bessner enters her cabin to investigate the body, it's pretty obvious he takes a step "down".