I was hoping this story would end differently and you just had a 'slow eater'.
I had the same nightmare issue with an entire clutch a few years ago.
Upon necropsy I noticed a congenital hourglass tissue formation in the esophagus that should not have been there.
Food would get stuck half-way in, and forcibly extracting the prey item resulted in heavy damage...ultimately leading to death.
In hindsight if I had known the exact issue I could have fed extremely small prey items, but, upon necropsy...too late...
I dread encountering this condition again and have completely outcrossed the original breeding lines to prevent this from happening a second time.