Intro image shows correctly in editor but exports as "Select Media" placeholder

I added an image overlay uploaded a photo via

Overlays → Intro/Outro → Selection of the "New Zeland" template.

The image displays correctly in the editor and video preview, see attached screenshot:

However, when I render the final video, the exported clip shows the empty "Select Media" placeholder icon instead of my uploaded image, as if the image reference wasn't carried through to the render pipeline:

Could you help me out?

Thank you, best regards.