TinyMCE not working in different context

Running MODX 2.5.7. I have a resource with rich text content and embedded images. Can edit just fine in the Web context. Copied this resource into a different context. Images display as clear boxes. Cannot even insert a new image into document. Why?

I go back to the original resource and I can edit the images, insert new ones, just fine.

Using TinyMCE RTE 1.2 (the new one). Also I had 4.3.4 - the older one - installed alongside beforehand, and had the same problem. I removed it and also removed the RTE 1.2 then reinstalled it.

If you want contexts to share same source/images, make sure the editor is returning fixed absolute full IMG URLs. (http and all)

Otherwise duplicate the assets folder that has the images.

In the MODX manager, right-click the image to inspect the source URL.
On the "frontend" do the same inspection.
You will see the cause of the discrepancy.

In TinyMCE, use: