Hello soapboxhero,
Thank you for using Apple Support Communities and for sharing these details with us. You’ve done a tremendous job in isolating this unique issue. From here, we’d like to recommend some additional steps you can try that could potentially help sort this out.
1.) Make sure your macOS is fully updated.
1.) Choose System Settings. Then click General in the sidebar, and Software Update on the right.
2.) If Software Update finds new software, click the Update Now or Upgrade Now button to install it.
3.) Enter your administrator password, if asked. During installation, your Mac might restart, and you might see a progress bar or blank screen several times.
2.) Follow these steps if your display is not detected or disconnects: If your external display isn't detected or appears blurry when connected to your Mac - Apple Support
If you continue to experience issues, try testing this issue in safe mode. Safe mode is a great way to isolate software issues as the root cause for this issue. Just in case, this resource can guide you through the steps on how to start up in safe mode: How to use safe mode on your Mac - Apple Support
Apple silicon
1.) Shut down your Mac
2.) Turn on your Mac and continue to press and hold the power button until you see the startup options window.
3.) Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”
4.) Log in to your Mac. You might be asked to log in again.
Depending on your results, please follow the steps listed under "If the issue continues in safe mode" or "If the issue doesn't continue in safe mode". We hope these steps are helpful. Thank you for using Apple Support Communities. Cheers.
