The universal nature of life (not just humans) relies upon the copying and re-copying of DNA continuously within ever cell of our bodies.
This process is inherently flawed. These "flaws" or mutations are the ONLY reason life has the capacity to evolve.
If the DNA replication process were "perfect" we, and every other living thing on the planet would have all died out millions of years ago.
Mutations - slight changes and differences allow some to survive an ever changing environment while others die.
Therefore, we are flawed by design, and with purpose. The mistake, error, or defect in life as we understand it, would be to be flawless - a survival impossibility.
So our flaws are not flaws, but a reflection of the perfection that we are.... flawlessly flawed.