"Send Ether" not working

I am using the "Ethereum Consortium Network Deployments Made Easy" template in Azure Gov and am having an issue with the "Send Ether". I used all of the defaults when building the environment, and it seems to be functioning correctly. The Bootstrap with the 1000 Ether works great, and the ether is immediately transferred into the MetaMask wallet. However, from there, when I try to send 15 ether to another account, it fails with "Invalid Sender". I have tried re--creating the entire resource group a few times, and this is repeatable for each time I've tried it.

Start by reproducing the Ethereum Consortium Network Deployments Made Easy template in Azure Gov with its default settings, then follow the Send Ether flow from the funded MetaMask wallet. Compare the successful bootstrap transfer with the failing 15-ether transfer; done means sending ether to another account succeeds without the “Invalid Sender” error.

Written by the indexing model from the issue text.