This is the second onside kick with 19 seconds left. Watch carefully how close the Cleveland player came to not only coming up with the ball but running it in for a TD. The Bills nearly blew another game.
That missing XP allowed the Browns to make it a one possession game at the onside kick. Of course the Bills D shouldn't have let it get to a one-possession game in the first place.
My analysis: rough start, defense woke up, offense woke up, it's the Browns, defense let up at the end and allowed them get to close in garbage time to the point the Bills had to get the onside kick to clinch it.