Plot hole: Anubis Warriors can only be killed by being beheaded. But during the final battle, you see several are killed by simply being stabbed.
Plot hole: The timeline is off. Mummy started in 1923, yes, but it wasn't until three years later in 1926 that Evie and Rick actually met. Mummy Returns takes place in 1933 - only 7 years later, but they've got an 8 year old son. At that, Rick and Evie's son was born the year before they met... (00:04:45 - 00:42:35)