How can a builder be safe in future after possession from contractor's mistake ?

Hi We are four partner's in a firm in Mumbai. We acquired a small plot and sanctioned a plan which has 20 (Residential Flats) Units and opted for lock and key construction contract, and gave it to a contractor and offered him 2 units (3BHK & 2 BHK flat) Residential flat in return to the total consideration value. Now the contractor has done sub standard work due to which there is leakage in the building. The issue which I am facing is my partners are insisting to hand over the flats to the contractor and let him registered and Release him from his work. Having trouble with my partners as well, all three of them are saying we will look out if anything goes wrong. and he (contractor) will repair with his own cost, But I don't trust them. They are taking full responsibility for HIS work. Legally what can be done to keep myself safe in future if anything goes wrong, I know our company will be liable but how can i be safe if my partners wish to handover the contractor his flat. From my point of view he has not fulfilled the work