Re checking of certificate while in service

Dear Sir, My sister got appointed as assistant professor in a central university (based in Uttarpradesh, in 2009) under PwD quota (OH) through her disability certificate, which was issued by a district hospital board in Tamil Nadu. Whereas, following appointment in the regular service, in reply to a complaint by a coapplicant, she re-verified her disability certificate from a Government Hospital in Lucknow (in 2010). The Lucknow hospital issued a certificate, which showed disability is higher(68%) than the Tamil Nadu District Hospital, which issued certificate with 45% disability. The same certificate (of Lucknow Hospital) was again submitted in the university office and the same has been accepted and given as reply to complainant. It has been eight years since then. Some one has again complained in the University questioning her disability. Now University authorities are again asking her to get re-examined her disability and justify the disability certificate. Whether the university has Right to demand again to get a fresh disability certificate of my sister, who got her certificate verified to the satisfaction of the University in the previous time.? This is almost an harassment as appearing with medical board is cumbersome. Request any one to kindly give answer and suggest necessary steps in this regard. Thank you in advance. Best regards, Kumar