[vRA 8.0] Error using ABX extensibility

Hello the community.

I'm currently trying to use the new ABX functionality in vRA 8.0 to do a simple thing, rename the VM before the provisioning.

First of all I create a new action based on the embedded script (I tried both Python and JS versions of the script)

Then I create a new subscription based on the topic compute.allocation.pre (which I guess is the right topic to rename a resource)

Finally I ask for a test blueprint to be provisioned. I can see that the ABX action is called in the "Action Runs".

But the blueprint systematically failed with the error : "Extensibility triggered task failure: Extensibility error for topic compute.allocation.pre: [10040] Image creation KJob is NOT completed!"

Does anyone succeed to deploy a VM customizing the name ?

Maybe I'm using the wrong way, but there is a serious lack of documentation about extensibility capacities, which if for me one of the most important part of vRA.

Thanks for your help !