I personally have a theory/headcanon that Bob has Myopia.
Now you could say, "Oh well, Beka, that's stupid," BUT LISTEN. This mother fucker has missed stabbing LITERAL CHILDREN.
This dumbass mistook meat for children. He only stops once they start MELTING. He couldn't even tell which one was the REAL skid and pump
Even in the car scene, he cannot reach them and proceeds to miss SEVERAL times.
"Oh but he's just fat." Sure.. but even a guy like him would know to just, reach in further. Unlesss he can't see them.
We have seen COUNTLESS times in spooky month drawings that Bob wears glasses.
"Oh but beka, how then would he kill his victims?" CONTACT LENSES.
All of the victims' dismemberment could even back it up since they probably took those out when they arrested him. And when you can't really see who you're murdering, you're more than likely to make a mess..
But yeah, just a mini headcanon/theory :P