Question: High Sierra partially dies
Since upgrading to High Sierra I had a recurring problem which I can't track down. After an arbitrary amount of time the system partially dies - Activity Tracker shows no content in any views, and I can't open Safari or Terminal to find out which processes might be causing the problem. Safari reports an Application not responding error but can't be opened, Terminal just doesn't respond but show no error. Other apps appear to be unaffected - Finder works OK, as does iTunes and Mac App Store. Other simply don't open.
Sometimes this happens after a few minutes after switching on, sometimes it's several hours.
The only way to resolve the issue is to restart or power down and restart.
I have tried reinstalling macOS but with no joy. I've looked at Console logs but really can't see anything and generally this occurs after a period of idleness so I'm not even sure what time to trace back to.
Has anyone else seen this behaviour or can anyone suggest a possible solution?
iMac, macOS Sierra (10.12.6)