This occurs when an edge server recieves a client request and must make a request to your origin, but your custom health checks are reporting the backend as down (and thus we do not even try). We currently have a bug where this error is thrown instead of "Backend.max_conn Reached" (see below). This only happens when the maximum connections is first encountered.
Thanks spuds, first thought was malware!
Both SAS and MBAM came back clean, but I think I've sorted it now.
My PC has recently been a bit erratic programmes slow and sometimes un responsive and memory usage very high.
Tried in Safe Mode and think that Samsung's Kies software was the culprit.
Now I've disabled it, my PC is running much better!
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