[away3d] z-sorting issue with ownCanvas

[SB]

I have a z-sorting issue related to setting ownCanvas=true on a group
of objects that I haven't found an answer for (despite there being a
number of topics on the issue).

I have a scene with multiple cubes that are set at different x and y
coordinates but all at the same z coordinate - 0. When a cube is
clicked it moves forward in the scene (towards the camera) and thus
"covers" the other cubes. In order to apply filters (specifically a
drop shadow filter) to each cube, the ownCanvas property is set to
true. However, when ownCanvas is set to true the cubes no longer
render correctly - cubes that are further back (at z=0) will appear in
front of the cube that is closer to the camera.

Here are a few screens showing the issue:
<a href="http://www.sic-culture.com/z-sort/z-sort_1.jpg";>Cubes before
sorting</a>
<a href="http://www.sic-culture.com/z-sort/z-sort_2.jpg";>Lower left
cube moved towards camera</a>
<a href="http://www.sic-culture.com/z-sort/z-sort_2.jpg";>Another cube
moved towards camera</a>

I've tried alternating between Renderer.BASIC and
Renderer.CORRECT_Z_ORDER.
I've tried pushfront (even though the issue is not intra-object
specific).
I've tried putting all the cubes into an ObjectContainer3D that also
has ownCanvas set to true.

Seems like a relatively simple problem. Any suggestions?