The minimal repro:

• Install powershell core, at least one of them
• Close the Terminal.
• Delete all the settings.json files.
• Open the Terminal, go to the SUI, go to the "Appearance" of the Powershell Core.
• Change scrollbar state to hidden.
• Hit Save.

At this point, the SUI will reload. The scrollbar state didn't apply, and now you've got a mysterious "Default" profile. Also, the setting.json is now corrupted. It's now got

{},
{
  "scrollbarState": "hidden"
}

slammed in the profiles list, which is garbage data.

• Figure out why the setting is blasting off to space.
• Add a mitigation to ignore profile snippets without a GUID

/cc @carlos-zamora.

Now, I'm gonna close all the threads we think are a dupe of this one.