Answer to your question in short is 'Disadvantage of bureaucracy'
Our policy is to check the steps for safety at the start of any program, which you have ignored in the beginning.
Secondly, rectify the same at any cost whenever such problems arise, and hence advise you to cooperate bank and resolve the issue. We personally cannot help you in any alternative..
One more suggestion: as seen from the change in Karta, the HUF seems to be your father's. So, legal heirs of your brother's family would not be required here. The list of all the beneficiaries who hold the rights in the HUF should be declared.