I have this theory that Kelsey is in control of the lonely Freddy doll version that talks to the crying child (Sammy as I like to call him) and he caused the springlock failure. My reasoning for this is he causes the Jaw to go off when Devon was searching for Kelsey in it,so why couldn't he have done it to the crying child.remember the tuft of hair in one of the suits from one of the minigames?

I think that's the hair that Devon finds in golden Freddy.