Neighbour only complaining but is not coperative for repairing work which we agreed to do

Hi. my father bought a flat in mumbai. it is found that there is serious leakage from his bathroom to the neighbours bathroom and bedroom downstairs. on his very first complaint my father hires aplumber and replace all the old pipes (as the building is very ol and has warn out iron pipes) with new pvc pipe. he spent almost 50 k. and also have proof of work done by photos and videos. now after 1 month again there is leakage in the neighbours flat. he is complaining again and society is asking us to resolve issue else compensate the da ages to the neighbour. My father did agrred to again do the repair work if the neighbour take responsibility to not to raise any complaint or hold my father responsible if th plumbing work is done again which will cost him 1 lakh again. we asked the neighbout to come along with his own plumber who is knowlwegebale plumber and take asssurity from his that the work he will do be 100 percent success. But the owner said he doesnot have time. and he also denied that he wont raise complaint again if after spending so much money and inconvinient work done while my father is already living in there and he is 80 yr old. What should my father do. Please tell some resolution as society very careless and without looking in to this issue always ready to charge the penalty for damages of neighbour in to my fathers maintainance bill.