the 'certificate code error' shown in eventlog, is due to the fact that the router is using a self signed certificate and if you use Chrome to access the router over HTTPS, the browser is sending an alert to the router that the certificate is not from a known trusted CA.
If you were to install a certificate on the router from a known trusted CA then this would not happen.
You can safely ignore the message, or you can filter it so it is not shown in eventlog anymore with the following command:
event 0 ev_filter 98
For other eventlog edit info you can see here: https://www.digi.com/resources/documentation/digidocs/90001019/default.htm#tasks/t_edit_event_descriptions.htm%3FTocPath%3DConfiguring%2520alarms%2520%7CEdit%2520event%2520descriptions%2520%7C_____0
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Digi Technical Support