My MacBook Pro (15-inch, 2017) running macOS Catalina 10.15.6 (19G73) will inevitably kernel panic while in sleep mode when my external display (LG Ultrawide 34UC98-W) is connected via an Apple Thunderbolt USB-C to Thunderbolt 2 adapter.

The issue appeared a few weeks ago and since then has become a daily occurrence. I am able to disconnect my external display from power via a smart plug but I generally forget to, and when I do I end up coming back to a MacBook that has panicked and restarted.

More recently, my MacBook has started waking from sleep correctly but not detecting the external display anymore. This is even more frustrating because no amount of fiddling with the cable or the settings will fix this. Only a restart will cause the MacBook to detect the screen again.

What can I do to stop these issues from occurring?

EDIT: Here is an example panic log.

  • I'm going to attach a panic log to this question next time this happens.
    – kettlepot
    Commented Jul 22, 2020 at 7:15
  • Is it possible for you to test the connection to the monitor with another cable & adapter?
    – IconDaemon
    Commented Jul 22, 2020 at 9:55
  • Unfortunately I don't have one available. Are you thinking the problem might be the adapter itself?
    – kettlepot
    Commented Jul 22, 2020 at 11:08
  • Testing the connection between the computer and a peripheral is a troubleshooting step I use to narrow down the problem. Although Apple cables & adapters are usually of the highest quality, they are physical objects subject to being damaged either out of the box or after use. If the setup works with a new cable/adapter, the problem is with the old cable/adapter. If it doesn’t, the monitor/computer is to blame. Because the problem recently happened, when it worked just fine before, leads me to think the problem may be the cable/adapter. A chain is only as strong as the weakest link.
    – IconDaemon
    Commented Jul 23, 2020 at 11:09
  • Thank you, I might try that. I've uploaded a panic log here: gist.github.com/gabrielecirulli/…
    – kettlepot
    Commented Jul 23, 2020 at 12:00

1 Answer 1


Surprisingly, Apple Support’s advice of resetting the SMC and NVRAM was actually the solution to this issue.

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