When using Evas 3D in Elementary, if you add a file based texture to at least one of the 3D objects, and there's more than one 3D object, after a couple of minutes, or after "unhiding" the window, all 3D objects will loose their textures. Some vanish entirely, some go black. "Unhiding" in this case means one of - move to some other virtual desktop, then move back to the one with the window, or iconify and uniconify the window. Doesn't do it when shading and unshading.
This doesn't show in the examples, coz they either have only one 3D object, or none have file based textures. The non Elementary examples don't show it, and some of those do have multiple objects with multiple textures. This basically makes Evas 3D unusable in Elementary. Add another object and some textures to any of the Elementary examples, and you'll see it.