Lindsay mentioned that the fingerprints of the 2nd Mac Taylor start at the 99th floor. However, in the very first scene, this victim is seen tugging on the 100th floor exit - where his fingerprints would have been found when the crime scene was processed.
Mac Taylor has a clearly visible scar above his heart, received when he was injured during the bombing of the the Marine barracks in 1983. However this scar is not evident during Mac's morning swim.
The team finds over 30 "Mac Taylor"s in New York City, with only one of them female, named Mackendra. Since 1980, the name Mackenzie for girls has been more popular than any other name beginning with "Mac" for either gender, growing in popularity each year. Odds are that most Mac Taylors in New York City were women and girls under 30 whose full names were Mackenzie Taylor. It is highly unlikely that nearly all the Mac Taylors in NYC were men.
When Adam and Stella are looking up their coworker's names (to see how many there are), they find just one person named Sid Hammerback, who is an elderly woman. There should have been two Sid Hammerbacks, since they work with one.