Oh, wow, that was a lot of fun 
. Took a little while, but a lot of fun nonetheless!
there are a few reasons for that - first, the occluder doesn’t have the root as a parent. Second, the scene needs to be prepared in 0 rotation and 0 position, if you want to just apply the transformation of the marker. Otherwise you will need to transform the scene correctly.
Anyhow, try this - Image Tracking Demo | Babylon.js Playground (babylonjs.com)
This is a screen capture of my test device (that had this silly out-of-focus issue, which made tracking fail for a bit). Still, you can see the effect, and how awesome it is. gives me so many ideas!!