Bda property in hsr layout

Hi All, We recently received a court notice requesting the court for a permanent injunction on my property. The property is purely an BDA and this was first allotted to an old lady on April 2014 (as an alternate site allotted by BDA). Since it is alternative site allotted by BDA there is no waiting period. There were almost 3 registration transaction including mine and all papers are accurate. I got the property registered in 2014 itself and all papers including Khata Extract, Khata Transfer, Property tax were transferred on my name. Just recently I had got the latest EC, new Khata certificated veriried all the papers are in my name. I even paid 2015 - 2015 tax on my name and even got the construction plan approved on my name few months back. We started our construction of work and we are in intiial stage of construction. We have a clear deed from first owner to even 3rd owner who is me. At this stage an unknown person who claims this property belongs to his grandfather during the year 1920 almost 95 years old. And he is claimng this site belongs to him. He has asked for permanent injunction and sent me an court notice that we are interfering in his property. I have cross verified my documents from couple of places including getting a latest EC and even in BBMP last month there is no chance of the papers of BDA can be wrong. Can anyone suggest what is the best approch. Can the BDA papers be wrong? please advise.