We had this for a long time. It was completely random with v8.1.
Problem was that when you get notified, it is probably already resolved. Status turns green on next refresh in console or on client with no action on our side. When you reboot right after notification, it is OK immediately.
I was trying to get logs, but it is uncatchable, there was a PC, where we had 5 incidents per hour, we started loging and it never shown again.
It calmed down almost comletely in recent weeks and I didnt see this warning on verison 9, but we just started upgrading (we skipped mass upgrade to 8.1 because of this).