Is the Paralympic sports system unfair to certain athletes with disabilities?

Designed to make competition between athletes with different disabilities fair, is the classification system for Paralympic sports flawed, easily manipulated and lacking credibility?
This show is not currently available on BBC Select but browse through the below titles for more documentaries available to stream on BBC Select.
Paralympics: The Unfair Games? on BBC Select
In this BBC investigative documentary, former Paralympic athlete Richie Powell meets other athletes and coaches, some of whom have jettisoned their dreams due to perceived inequality. Could the system be fairer?