Need advice on land dispute

About 40years ago, my grand father has exchanged land with others..and it’s handwritten on paper and was not registered.We got 3acres 6 guntas(actually 14 guntas).He denied registering it though my father suggested to do. It came to my father after they distributed property in 2004 or so. Somehow, in records, the survey number got interchanged with neighbor landowners by mistake. My dad requested them multiple times to collectively correct this survey number issue, but they denied.My dad reached out to MRO office to make the correction and MRO has corrected it after sending notices to neighbor parties. They did not take notices at all. Finally correction was made in 2006. In 2010, one of five neighbor parties filed complaint in RDO. They are farming their land as per their correct survey number land borders. They have not done agriculture in our land though they did some provoking activities. Also, while this appeal is in court, they have got their lands registered.RDO has cancelled the case this year seeing all the evidences of my grand dad’s Hand written Paper, Pahani, and other documents on my dad’s name and his appeal for making correction earlier. My dad applied for issuing new passbooks in MRO, they are objecting it, saying that land referred is not my dads.And they are not even telling what they think is my dad’s land then.Their main intention is to make my dad withdraw hopes on that land and leave it for them.He is 67 years old with lot of health problems. We don’t want him to make trips to these offices and bear the mental tensions as he is on continuous daily medication. How can we proceed to fix this issue considering his age, physical and mental health.?Thanks in advance..