There are no components above the label ("Bluetooth Real Ambient Node Data...") in the flex container, and the caution sign does not appear when in Preview mode in the designer:
Any idea why this would be?
Check for a top docked view in the page configuration settings.
Could be either page-specific or in shared settings.
Could you have bind something to an non-existing header? Perspective > View
It could possibly be a Perspective docked view which is configured incorrectly. Have you checked there? Docs