What is the name of your state? NY, although the POA was drawn up in Ma.

My dad has named my mom as his Attorney in Fact through a normal POA document. Last month, my mom resigned her POA for him, and passed her authority in this regard on to me via a regular POA resignation one page witnessed and notarized form. My question is, since the original POA document naming her as his Attorney In Fact still exists, can she endorse a check for deposit made out to him by signing her name as Attorney-In-Fact for him, and then depositing it in their joint bank account? If anyone asks her for proof that she has this POA for him, she can furnish copies of the original document naming her as the Attorney In Fact which still exists and is alive and well.. In other words, when she filled out a poa resignation, she didnt have to give up the original document naming her as his Attorney In Fact.

The situation is this.. They are both in their mid 80s. Hes terminally ill in a facility; shes still living in the home, but is weak and has memory issues. Shes still trying to live independantly but is having some difficulty with memory issues, etc. They have a joint checking account, and shes been depositing checks made out to him by getting his signature, but hes getting too week to sign. Its a question of logistics. She could mail the check down to me as she resigned her poa to me; I could sign it as his Attorney In Fact; send it back to her to deposit in their joint acct... Or, she can just use her original POA document to support her endorsing of that check to deposit. Since she still has the original document naming her as
his Attorney In Fact, plus the separate one page document resigning her POA for him to me, couldnt that allow both her and me to sign for my father? After all, all that anybody ever seems to require to allow her to sign for him is a copy if this POA which she has in tact. If she doesnt use the resignation document and keeps it tucked away,
then the bank or the payee doesnt know it exists, so what is the harm in her endorsing?

If this cannot be done, is there any way that both She and Myself can be Attorneys In Fact for my Father? She should have it so she can endorse checks made out to him and deposit them in their joint account. I should have it for signing any papers more complex than that, ie, for the sale of their house which is in his name, or the handling of his investment accounts, etc. So ideally, we should both have the POA for him. Can we manage it as I suggested, ie,

1) with me using her resignation of her POA for him to me, and
2) with her using her original POA document from him to her?

Thank you.