For FQDN objects (which you're clearly using), the gateway periodically queries the configured DNS resolver to find its IP for proper enforcement in the Access Policy.
The Occam's Razor answer is, therefore, at least in your DNS resolver (if not globally), bierbuducunpderdr[.]ddns[.]net resolved to that IP.
Once that FQDN stopped resolving (it currently doesn't for me), the problem resolved.
How bierbuducunpderdr[.]ddns[.]net resolved to that IP would be a question for the folks who run DDNS (No-IP).
