Continuity mistake: In the first film, "Red Pyramid" is portrayed as absolutely massive. (Judging by the scene in which he rips a cultist's skin off, he is about 10-12' tall) Yet, as evidenced in the final fight sequence, he appears to be significantly smaller in this film. (7-8' tall).
Continuity mistake: At the end, when Claudia transforms into the final creature after touching the seal/amulet, her human body begins to disintegrate. As she screams and the scene cuts from a medium shot to a closeup, all of her hair suddenly vanishes between shots.