Hi Andy,
That is most likely your problem. You should change it to a different port number and forward that
port instead. Address your RRC with a colon following the URL, e.g. rkdgt793.ddns.remoterig.com:XXXX
where XXXX is the new port number. I am pretty sure that your problem will go away then.
73,
Mitch DJ0QN / K7DX