Buyer not honoring the sale agreement and not agreeing for cancellation

We (myself and my father who is a senior citizen)( as a seller) had entered into an registered sale agreement (through registered will) for a plot with the buyer (4 partners) in Sept 2023, advance payment (15% of total sale amount) was made by him through NEFT for the agreement and 6 months time was given for registration. It ended on March 2024 but the buyer gave the reason of amount has not arranged and asked to extend it for another 5 months (i.e.; August 2024) and the extension was also made through registered agreement. Further in August August 2024 but the buyer gave the reason of amount has not arranged and again asked to extend it for another 3 months (i.e.; November 2024) and the extension was also made through registered agreement. But In November 2024, his one partner is ready to execute his area and no other 3 partners came, but there is no specific breakdown of property sides, i.e.; which side to be given to whom, therefore the specific area registry is not executed by registrar. Further, on the last date of agreement I had present at registrar office for registry but no one came except one partner and i have given attendance twice a day (i.e.; in morning and at evening). and one partner also gave attendance at registrar office. But now the buyer is saying that i will not come and i will go for legal action. Can he go for legal case on agreement or registered will? We are ready to pay back the the full amount given by him as advance and go for the cancellation. I have read in this forum that the cancellation should be done mutually but what happens in these scenarios. We have sent a legal notice through a lawyer (registered post) on November 1st week and stated that please execute the registry and give my balance amount. He has not given any reply till now and still says in the phone call that he will not come. My father who is a owner is a senior citizen, if it goes to court it will be very difficult for him and to go through the court proceedings and we will not be sure how long does it take to get the judgement for these cases and we are in need for the money for some other commitments. Other People are ready to buy the this guy is not signing the cancellation agreement. is there any other way we can resolve this issue, we are ready to pay the full amount given by him as advance. Can we give a police complaint ? Please help us in this regard.