A nonzero value here suggests something other than a well-behaved RADIUS authentication server is responding on this port, for instance a firewall or NAT device sending back unexpected traffic, or a misconfigured server sending accounting-type packets to the authentication port by mistake. The admin should investigate this as a configuration or network-path anomaly rather than a normal auth failure. For example, this counter incrementing right after a firewall rule change on the path to this server would point at the new rule inadvertently redirecting or mangling traffic rather than at the RADIUS server itself.