Hello.
A KMZ file contains images that are displayed in the popup (JPG or JFIF) and images (PNG) that are used for symbology. The images are not regrouped in folders. The images used for the popups are displayed using CDATA in the <description> tag of the placemarks. Everything displays correctly in ArcGIS Earth.
The KMZ file is then saved as a new file with ArcGIS Earth. By doing so, the images used for the symbology are automatically regrouped in a folder named “files”, and the images used for the popups are regrouped in a folder named with 10 characters of seemingly random numbers and letters.

The doc.kml file is edited by ArcGIS Earth so that the styles will now use the new path for the PNGs (<href>files/….png</href>). The symbology remains the same.
But the image sources in the CDATA (<img src="…">) are not edited by ArcGIS Earth with the new folder path. Because of this, the images in the popup are all broken.
Earth should either not regroup the images in a new folder or should update the path in the CDATA.
Thank you.
Geoffroy Richer-Lalonde
GIS Specialist, Hydro-Québec