Thinking a little bit further, I wonder if the problem is the time it's taking for WMI to initialize the new partitions... meaning that when the application checks for them, they exist but Windows hasn't yet established how big the new partitions are.
Of course, I'm asking here rhetorically as I wouldn't expect you to know the answer - but I've noticed the logs do not contain any useful information about the partition sizes it creates after wiping the disk, which would (in this case) be handy. But, if after shutting down the application, and starting it again, it's still showing the partitions as 0 bytes - then this suggests something has failed either in the partition creation, or the application thinks that partitions it is creating really are 0 bytes (which may be some underlying problem with the disk)