So far I have tried to swap out all paramaters being passed to New-VM with something else (VM name, template, specification, datastore, host, etc). However, I consistently get the error when creating the first VM. Every time after that I can use the same parameters with a new name and it works fine repeatedly until I disconnect and reconnect. Same occurs obviously if I close PowerShell and start a new console too.
I have opened up an SR on the issue, but would still be interested if anyone has any additional feedback on what to look at in the meantime.
Thanks again!