No Chain of Agreement between previous owners before completion of flat.

Recently i bought a property and i took loan from NBFC after lot of struggle finally i got a loan. Today NBFC is charging huge interest rates hence i plan to shift to Banks. Story below : In my case, a society was formed earlier by a group of people coming together. They got a contractor in place and started construction. Society got permission for 4 stories, but due to lack of members (investors) to pay money to a contractor to develop a flat (i.e. self-development by society) they stoped construction till the 3rd floor, 4th floor never came into the picture. Society was formed in 1972, construction started later around 1974-75. 1st owner of the said flat, (when construction was started and even flat was not ready) sold his flat to 2nd person in 1978 and 2nd person sold same flat unit (which was yet to be constructed, as the building had just finished making of 3rd floor). Due to the slow pace of work, he sold his flat to 3rd person. Now 3rd person occupied this flat by the end of 1979 when building work got completed and he became absolute owner of the flat and previous seller never did the chain of agreement as the flat unit and entire building never existed. Due to self development by society members, society did own work of CC, OC without builder in place. Now in 2019 when i purchased i became absolute 2nd owner of the flat and got registered in Index 2. Today for re-transfer banks keep asking for Chain of agreement among previous owner, but it doesn't exists due to no actual flat unit in place and in 1972-79 building came under Nagar Palika, and registration happened only in Fort, Mumbai. No such laws existed for complusory chain of agreement not stamp duty registration till 1980 until Hon. Bombay High Court gave verdict in favor of flat buyers. What should i reply to banks while applying and resolve this to get easy clearance of home loan.