Deleting from the syslog appears to cause some instability when logrotate kicks in. After the attempt to rotate logs, no further entries are appearing in the syslog (although the timestamp is still updating)
Look to use solution offered in https://forums.unraid.net/bug-reports/prereleases/6xx-rsyslog-filters-do-not-affect-local-syslog-r1230/ which is to add strings that should NOT be logged to /etc/rsyslog.d/02-custom.conf