1. Anybody can claim anything which you can not stop. I find no merit in his claim,
2.The Bank also be a party to the case and there will certainly a direction upon the Bank to refund you the amount with interest and cancel the sale conducted by the Bank,
3.It is your responsibility also to conduct due diligence about he property. Since the will is not probated, it has no value other than a scrp paper,
4.Contest the case fittingly,
5.There is hardly any chance that you will loose the case.However, if you loose,you should claim all your expenses on the property including registration cost.