Avid DNxHD alpha error

I have been learning Fusion Free and have found it a really powerful program, thanks BMD!

However I have found an error with Avid DNxHD rendering and saving. The alpha channel does not export properly no matter what I do or set. When importing the resulting file into Avid MC 8.3 the Alpha channel is just black.

At first I thought it was something I had done wrong in either or both render3D or saver nodes, but both Quicktime animation and TGA export correctly. I then looked at both general and project Quicktime settings. Same result with DNxHD set to alpha compressed or uncompressed.

I feel this could be an Avid codec issue rather than Fusion but I thought I'd ask here first to see if anyone else has had the same issue and whether they have solved it?

I realise that I can use the AVX Connect plugin, which works well, apart from not automatically launching the comp, but there are times when I want to devote all system resources and memory to Fusion without having Avid open at the same time.

I'm surprised there's been no response to this from Fusion developers, I would have thought that DNxHD is a pretty important codec. I do quite a lot of 3D with Alpha, taking models to incorporate in other scenes and I'm finding Fusion far more responsive as stand alone than using Avid Connect.

I've tried both 8 bit and 10 bit with the same issue: the Alpha channel is just black.

As I say Tiff, Animation and PNG etc. Quicktime all work with the same Saver/render settings. But as I understand it only Tiff is capable of 10bit? In the saver settings though I'm only able to select a maximum 32bit, which I assume is 8bit in videospeak (the three colour channels + the alpha) whereas DNxHD allows for 64bit?

Any clarification on this would be much appreciated.