Release deed for mortgaged property

Hi, We are planning to buy a house in Gurgaon, Haryana. The owners are husband and wife, they both live in USA. The husband maintains an NRI status whereas the wife maintains an Indian resident status. The property price is 2 cr and it has a pending loan of 1.2 cr. The loan was taken under NRI loan housing scheme in the name of husband, probably has wife's name as well in the loan. We offered to pay off the loan and make equal payments to both sellers. But they insisted on transferring the entire amount in the wife's account to avoid paying 20% TDS. We refused to do so as it may put us at risk for not paying the TDS correctly to tax dept. They then offered to execute a relinquishment deed to transfer husband's share in the name of wife. Although I am not sure if this is allowed without getting an approval from bank since husband still has liability on his share of property. Will the sub registrar even register such a deed without original documents or a letter from bank. They are claiming that its doable, we are not sure. Please provide your expert advise and how should we proceed on this.