Treatment of immovable property of dissolution of partnership firm

A partnership firm purchased an office for their business. Later 1 more partner was added and after few years they decided to dissolved the partnership firm where 1 partner would carry on the business at the above mentioned office as a proprietor after settling all the liabilities as on date of dissolution and settling accounts of the other 3 partners by paying them. This dissolution happened w.e.f. 31/03/1987. No registration was done as it was unregistered partnership firm. My question is does the property automatically go to the sole proprietor or any registration and stamp duty for the same has to be paid? The sole proprietor passed away in 2021 and his legal heir has applied for transfer of property in his name under Probate of Will. But the society lawyer has objected stating Stamp Duty on transfer of property from firm to partner will have to be paid first, only then the inheritance transfer can happen. Kindly help Question - Was stamp duty payable when dissolution of partnership happened?