The re-install should have eliminated the OS or anything in the OS as a problem.
Anything other than a bug, that is.
I'd revert to 10.14.5, but going backwards is more of a PIA than I care to deal with, particularly since the issue is only an intermittent nuisance, not a tearing-my-hair-out thing.
So now it is back to Old Fashioned Troubleshooting101.
- This sounds like something is momentarily tying up the I/O subsystem. Eliminate possible hardware problems by disconnecting as many external devices as possible — especially USB devices — and if the problem goes away try reconnecting them one at a time until the problem re-appears
- The next thing I would do is run Etrecheck and see if anything suspicious shows up in any of its reports. If you have Etrecheck Pro, pay particular attention to any performance issues and especially the detailed performance reports.
- boot from a test account and if the problem goes away it is likely something in your Startup items, or ~/Library/LaunchAgents
- If the problem still exists in the test account — try a Safe Boot and see if the problem goes away. If it does then look at /Library/LaunchAgents and /Library/LaunchDaemons for potential culprits
Thanks, but...
1. No external devices connected.
2.EtreCheck (non-Pro) doesn't show anything out of the ordinary.
3. & 4. Neither test account nor safe boot is a viable approach, because the freezes are so few and far between that I'd never be certain whether none happened because of my boot state or because none happened.
I'm going to keep working with Activity Monitor open and see what I can see; it's just occurred to me that the process at the top of the CPU column immediately after the freezes end (AM freezes too.) may be my culprit. (If I find consistency I can file a feedback report with Apple.)