Three pyramids were seen in the first landscape shot. However Osiris was supposed to be the first mythological pharaoh of Egypt. Moreover, the first pharaoh to have a perfectly shaped triangle for a pyramid was Sneferus, whose reign was estimated to be from around 2613 BC to 2589 BC, or the Fourth Age of the Old Kingdom.
Characters use a telescope, which was technology unknown until the Renaissance. Furthermore, if both lenses are convex, which they appear to be, it's a Newtonian telescope and should have produced an inverted image.
During Set's assault on the rebel gods, his troops are shown using trebuchets which wouldn't be invented for centuries. Trebuchets first appeared in China in the 4th Century BCE and wouldn't be seen in the Middle East for nearly a thousand years after that.
The first time Ra makes an appearance he is sharpening his spear on an angled wheel used on a step-grinder. The step-grinder is a relatively modern machine; while not new it dates far less than 200 years ago, much less than the thousands of Egyptian mythology.
After Hathor and Horus get out of Set's pyramid, Hathor puts her left hand to the side of Horus' head. When the camera is looking at her two of her fingers are on Horus' ear. But when the camera is looking at Horus, all of her fingers are below his ear. This happens repeatedly.
When Horus, Hathor and Bek are walking in the swamp, the water level comes to just under the knees for all three. Since Horus and Hathor are bigger, if the water level is below their knees it should be at least waist-level for Bek, but it comes to just under his knees as well.
When Horus, Hathor and Bek are walking in the swamp, Hathor throws her flask to Bek to get her fresh water but the flask gets smaller when it is in the air and in Bek's hands - then when he tosses it back, it gets larger again. Of course, it should be about twice the size when Bek has it and smaller when Hathor has it.
In Thoth's Library where Horus assaults Thoth, all of the Thoth's doppelgangers draw their swords with their left hand. For some reason, the editor chose to then flip the video to show Thoth holding the sword in his right hand for the next cut. However, all of the doppelgangers are holding their sword in the left hand in all of the remaining shots. You can also follow how the fern (along with everything else) jumps from left to right and back again on the table in this scene.