No matter how strong a fortress was, it would have a weakness. What more when it came to humans?
To a certain degree, biological bodies and mechanical bodies bore some resemblance. If something was wrong with one part, it would most likely affect many other areas.
In a mechanical body, the loosening of a screw could destroy the entire machine instantly. Similarly, if one function in the human body was not working, it might bring illnesses that could eventually take the life of a person.
Mechanical bodies have inevitable weaknesses, as do biological bodies. Naturally, humans, as one of the latter, are not spared of this. In reality, humans are one of the more fragile forms amongst the biological bodies as these weaknesses are even more fatal if exploited.
