Use page placeholders from Application Customizer (Hello World part 2) tutorial - top header disappearing

[kdengel]

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

• browser version
• SPFx version
• Node.js version
• etc

Describe the bug / error

Followed tutorial at https://learn.microsoft.com/en-us/sharepoint/dev/spfx/extensions/get-started/using-page-placeholder-with-extensions.

The bottom header sticks but the top header only shows for about a second and then disappears. I am seeing error messages in the console saying 'Refused to get Unsafe header'.

Expected behavior

Expected the top & bottom header to be present.

Thank you for reporting this issue. We will be triaging your incoming issue as soon as possible.

[github-actions]

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