cn=Proxy Userentry, you can work around the problem as follows:
You can temporarily add a second password to the proxy user entry so that you can transition all of the proxy server instances to the new password. However, you should have multiple passwords on the
cn=Proxy Userentry for the shortest time possible.
If you do not know the clear-text value, then you can use the encrypted value when configuring the new Directory Proxy Server. The encryption scheme allows reversible passwords that are stored in the server configuration so that they can be decrypted by any server instance.
You can create a new root user in the directory server instances with the appropriate set of privileges and have the new proxy server instance use that account to authenticate. Since it is not a good idea to have an account for which you do not know the password, you may want to update all of the other proxy server instances to use the new account.
You can use a protocol analyzer like snoop or Wireshark, to capture the password from the network communication.