OC Deposit refund Issue ?

Hi Sir, I have purchased property from Arvind Tambde 4 yrs ago and have signed all the legal sales agreement and transferred the sales certificate to our name. 1) The property is not having OC. 2) Society has collected OC money from Mr. Arvind Tambde before I purchased the flat. 3) The society finally decided in AGM to return back the money for the OC to the existing flat members as the BMC is not ready to give the OC certificate the building. 4) I have received the deposit money for the OC Now Arvind Tambde claims that the money was paid by him before we purchased the flat and he is liable to get the benefit of refund of the deposit. He has filed a legal case against us and society to return back the money to him as it was an extra payment which the society has collected from him. As per agreement it states that. All the amount standing to the credit of the vendor on this in the books of the society towards deposits such as authorized share capital, subscribed share capital, loans, security deposits, sinking fund with interest, dividend on subscribed capital, and other amounts to which vendor / transferor is legitimately authorized in respect of transferor being members of the society shall be transferred to the purchasers for the said flat mentioned above and making full payment. Please advise if I need to payback the money to the previous owner and what is the possible out come of the case if I go ahead and fight for it. Regards, Malav Vora