An admin seeing this increment on the login-authentication server specifically, distinct from the base client or accounting tables, should suspect something on the network path used for administrative access in particular, for instance a management-VLAN firewall rule interfering only with login traffic and not with other RADIUS traffic that might take a different path. For example, this counter rising only on the login table, while the accounting table's equivalent stays at zero, would point toward something specific to the login-auth traffic's path rather than a problem with the RADIUS server itself.