I've seen the error but only when it wasn't working period.
FYI the 127.0.0.1 IP is due to the architecture of the RADSEC. The APs use some sort of proxy in their code to implement RADSEC, so the dashboard will show the localhost IP instead of the actual IP. It definitely confuses troubleshooting. The error could be within the AP RADSEC functionality or still be a normal error with connectivity or your RADIUS server.