Second purchaser under paid the stamp duty of the Flat property

First purchaser from the Builder (Through Booking while on construction of the Building)had paid the stamp duty and got registered the property in year 1994 The second purchaser who was Constituted power of attorney of the first purchaser had bought the flat from him on executing sale of agreement. He has under paid the stamp duty and not registered. The deal happened in the year 1997 I being the third purchaser had paid the stamp duty fully and got registered the property in my time through electronic System in the year 2004. The sale deed happened in the year 1997 and the stamp duty paid then was part i.e. Rs.6,080/-. In the year 2004 I have paid the balance amount of Rs.29,050/- got the registration of the said flat in joint name with my wife. My question is that I am going sell my flat and the agent of the prospective customer has informed me that I should arrange to pay the balance part of the Stamp Duty of the second Purchaser before the flat is sold to his client. I am member of the Society and having my Share Certificate from the Society which transcends from the 1st Purchaser on the first page, second and third purchaser on the reverse of the certificate for transfer of flat in order of the sale of the said property duly signed by the Hon Secy.under the rubber stamp of the Society. Could you please advise in the matter. Thanks Sanjeeva B Shetty