Apple has pulled the High Sierra and Sierra 2019-004 security updates today as a result of many users having problems with their updated Macs. This has been reported specifically in recent MacBook Pro models, such as the 15-inch 2017/2018.
Apple has now also drawn one of the BridgeOS updates needed for the Mojave 10.14.6 update for some Mac models. Therefore, users who have not used one of these recent updates wait wisely now for Apple to address these issues properly.
Users report that adding an affected MacBook Pro to sleep, for example, by closing the lid, causes it to suffer a core panic and restart. The only solution to this, other than preventing it from hibernating, is to turn off the Mac instead. Which is not what you bought a MacBook Pro for.
If your Mac is affected by this, contact Apple Support, who will now reach what happens and when the fix comes.
The standalone installers for these have now been withdrawn, the previous pages gave 404 errors.
Thanks to Jeff Johnson @lapcatsoftware for the alert, and to Al Varnell for reporting that Sierra and BridgeOS are also affected.
(Updated 0600 UTC July 25 with BridgeOS News.)