Stamp duty paid but registration not done for second owner

Hi, I've bought a property in Mumbai of which I'm the fourth owner. The flow of possession was as below - 1983 - 1st owner - stamp duty paid, registration done 1990 - 2nd owner - stamp duty paid, registration not done 1999 - 3rd owner - stamp duty paid, registration done 2010 - 4th owner - stamp duty paid, registration done While purchasing, I had done all the checks as well as gotten a home loan for it from HDFC but the documents had been shown to be clear. However, recently when I was trying to transfer my looan to SBI, I was made aware that the second owner might not have registered the document. What I would like to know is - 1. What effect can this have ? 2. Will it pose an issue when I try to sell my property ? 3. What can I do to correct this ? I've no idea where the second owner is and whether he is alive or dead or anything. Kindly advise.