Our understanding is that the Rep Payee is fully accountable to the Social Security Administration when they take on the responsibility. Our responsibility is to be sure we collect the correct information from the Rep Payee when the account is requested. If there's any liability - it's most likely on their part - assuming we've followed our due diligence.
In the case of an entity being named as Rep Payee, we do ask for a letter or other document indicating who the authorized signers will be, just so our people know whom to expect as a signer. This information is placed on an account message for all to see.
You should know, too, that the SSA does not recognize Power of Attorney. POA is over the individual, and the Rep Payee has sole responsibility for SSA funds for that individual.
_________________________
Opinions are mine and never to be taken as legal advice!