Removing deceased parent from joint account

My mother recently passed away and everything goes to my father, based on her will, he is also the executor. I am the POA for my father because he has severe dementia and is in a home.

My mother, father and I have a joint bank account. I am joint so I can do all of their banking for them.

I tried to remove my mother from the joint account because of her passing. The bank is saying that my father has to be present in meetings with them, or he needs to renounce being executor with a witness of a lawyer. My father is not of sound mind to meet with the bank.

Is it correct what the bank is asking for? I have closed her accounts at other banks and they have not asked for this.

Bonus question, can I just leave my mother as joint on the account even though she has passed sway? I don't need to change anything with the account, and everything works.