Transfer of Vehicle Ownership Mumbai Andheri RTO MH02

I sold my car in 2015 to a family and they have still not transferred the car in the intended persons name. I moved to UAE for work in Dec 2016, then after a while he contacted me again stating that he lost papers and he approached me requesting to sign them again. I did the needful trusting this time he will do it. Buy he he still hasn't done it and now he is contact me again in 2021 for signing the RTO transfer papers. How can I trust him that so far nothing wrong has happened from 2015 from the date i sold until today 15 Feb 2021 with the car or no legal activities have been carried out. Or that the car has no claims or has no police cases. I am okay to sign and help him again but how can I make myself safe this time and not own up any claims, illegal activities or police cases from the day I sold it to him in 2015. Please advise and help me with solution to this. What should I do now sign and help him transfer it or not to sign on the documents as since Nov 2016 I am out of India and have been visiting my mother only on short vacations.