Other mistake: At the end, we learn that the predators are escaped patients from a hospital, ostensibly horribly mutated survivors of the accident. But if they've "escaped" into Pripyat, the hospital must be located inside the exclusion zone, and why in the world would they use a hospital there? All patients and staff were evacuated from the Pripyat hospital on April 29th 1986.
Suggested correction: The exclusion zone is only 30km. A hospital could have been built or other structure repurposed outside of the EZ. Simply walking at a normal pace, one can easily traverse 30km in a single day. Also, it's not an actual hospital that treats sick people. It's a clandestine operation to perform experiments on these mutated individuals.