An older Content Tree chart does not seem to be rendering all article images as expected. However, after I created a new Content Tree the articles which have Cover images do display correctly. I have embedded both charts to the article displaying them and you can see that the older chart doesn't display "Chinatown" where the new chart does. The "Hotel Baudelaire" displays the Cover Image as expected on both charts. Both article's cover images have been there for a month or so. I further have confirmed it is an issue with the older chart as I added a brand new image to an article that did not have a cover image before, Triggered, and it displays on the new content tree chart, but not the old one.
1- visit the article page, 2 - view the two charts, 3 - notice that "Chinatown" cover image is present on the top chart, 4 - notice that "Chinatown" cover image is not present on the second chart under "Old Chart"
I was able to mess around some more with settings. It appears that if you also add a cover image to an article after it's already been added to the tree, then it does not automatically pick up the image and assign it in the content tree chart. You will need to go into advanced settings within the content tree item itself and manually update to reference the image. However, if an article is added to the chart and it already had the image assigned to the article cover, then it will automatically associate to that image in the content tree chart.
Ah yes - that is on purpose. Content tress start with the information given by the article but decouple on purpose afterwards to give more flexibility to create menus or alter them visually. This is not a bug this works exactly as intended.