In the first movie Contracted (2013) Alice told Sam on the phone that the police caught B.J. on Day 3, but in this sequel they are still looking for him.
Between the first and second movie the way Riley gets infected is confused. In the first movie he's wearing a shirt while having intercourse with Samantha. In the second movie in a "flash back" Riley is shown to be not wearing a shirt.
In the convenient store Riley's nose bleeds down to his mouth and onto his teeth then it cuts to him with the blood only on his lip.
When Riley is examining the scratches and sores on his back, the scratches start on the upper right side but move to the upper left side after a cut then back to the right side.
When the detective arrives to the suspects house on Center Drive you can hear trains in the background, yet there's no track or line over there (lived down the street since 2004).