Hallo,
 i'm using radius+mediaproxy and since I moved my sip proxy on a public ip I have the folowing problem. I log in regulary and make my firs call with no problem. But When I hung up, and after few minutes call again, my proxy wont authorise me. I get a message that I need to authorise with proxy. During that my FRERADIUS is recieving requests for authorisation. The second i get rejected i call again and it connects me.
 I tried lowering nat_ping intervals but no succes.
 
my Invite snippet is a common one:
 
        sl_send_reply("100", "Trying");
 
        if (!radius_proxy_authorize("")) {
                proxy_challenge("","0");
                break;
        } else if (!check_from()) {
                sl_send_reply("403", "Use From=ID");
                break;
        };