the problem in this case is that one of the sites requires "secure site to site transfers" and the other doesn´t ..
i get "[L] 522 You have to turn on secure data connection."  trying the setting u suggest ...
Site1 : Auth TLS
          Secure File listing
          Secure File transfers
          Secure Site to Site transfers
Site2   Auth SSL
          Secure File listing
          Secure File transfers
          Secure Site to Site transfers
Site3: Auth SSL
          Secure File listing
1 -> 3    "You have to turn on secure data connection."  
2 -> 3    "You have to turn on secure data connection."  
disabling Secure Site to Site transfers on 1 or 2 doesn´t work either
would be lovely if u could make some sense of this 
