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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.

kettlepot
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  • I'm going to attach a panic log to this question next time this happens. – kettlepot Jul 22 '20 at 07:15
  • Is it possible for you to test the connection to the monitor with another cable & adapter? – IconDaemon Jul 22 '20 at 09:55
  • Unfortunately I don't have one available. Are you thinking the problem might be the adapter itself? – kettlepot Jul 22 '20 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 Jul 23 '20 at 11:09
  • Thank you, I might try that. I've uploaded a panic log here: https://gist.github.com/gabrielecirulli/135e855093313bfd015e9b513a18f02d – kettlepot Jul 23 '20 at 12:00
  • You might try resetting NVRAM or PRAM: https://support.apple.com/en-us/HT204063 – IconDaemon Jul 23 '20 at 13:00
  • The panic report indicates an issue with Thunderbolt. Disconnect the monitor and put (or wait for) the system to sleep. See if the panic continues to occur. Also, the adapter may be insufficient - Thunderbolt 2 requires an active connection and I've seen monitors and storage not work with the Apple adapter. – Allan Jul 23 '20 at 13:24
  • Interesting point WRT active connection. My external screen is usually on and in standby mode when the issue arises. I do have a smart plug connected to the screen which I use to turn the screen off entirely at night (or it periodically flashes a bright screen). However most of the times that my MacBook has panicked, the screen was on and the cable connected. – kettlepot Jul 24 '20 at 09:37

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

kettlepot
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