I've not seen this problem reported for VMware based AVA-v. I am suspecting there must be something unusual with the hypervisor. What version are you using of VMware, and what version of AltaVault are you deploying? What was the size of the 2nd disk added to AltaVault? Can you try redeploying the AVA-v image to another VM, and then try adding a small disk (say, 200GB) and see if it boots properly?