When a node reboots, Network Observability takes a while before recovering.  The console plug-in continues to use the old certificate so it isn't able to access Loki gateway.  I've seen it take more than half an hour before recovering.

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A node may be rebooted intentionally.  For example, if you need to make a machine config change such as https://github.com/sustainable-computing-io/kepler/blob/main/manifests/config/cluster-prereqs/51-worker-kernel-devel.yaml, it will cause a reboot.