My male cinnamon pewter did this once.. he was refusing to eat anything but live so I put the small rat in and he grabbed it and coiled and started eating right away but he was trying to eat it from the butt not the front so when the rat woke up it bit him on the top of his head and I didn't know what to do... he did end up eating it and he has a small scab that is getting smaller with every shed but I'm still traumatized by it and keep a close eye on him every feeding and it hasn't happened again I don't know why he started eating before it was killed that time. He's my last that still hasn't switched to pre killed, which is ironic because he was my first bp that I got when I got back into snakes.