Registration missing for old property

I'm planning to buy a flat which was build around 1972. The original buyer didn't have any agreement but has his name on the share certificate. The property was sold off in 6 months to current owner. Again, there was no registered agreement but just a form of transfer submitted. The new owner had the shares transferred to his name and still continues to be the member. (Conveyance is in the name of society) The prime motive of buying this flat is to benefit from the redevelopment of the building. But as I understand, I could get into trouble during adjudication process if all the previous agreements/transfers were not registered. But the current owner has clarified that since both the transaction happened in 1972, there is no question of fine/fees/issues. The current owner just has the form of transfer letter between him & previous owner and the society share certificate. Can you please help me understand whether there will be any kind of complications arising during redevelopment or otherwise that I need to look at?