Deploy provisioning templates with Azure Automation, PnP PowerShell Apply-ProvisioningTemplate error

I'm transferring a local script hosted on a PC to deploy SharePoint Site Collections and provision the root site using Office Dev PnP to Microsoft Azure. I want to deploy this script inside Microsoft Azure, so we can multiple users run the script to provision sites.

We know the PnP Partner Pack 2.0 exists, but this came a bit too late for this project, so we decided to build this using a SharePoint list and multiple Azure components. Everything works except the PnP PowerShell Apply-ProvisioningTemplate.

Inside Microsoft Azure, associated to the Office 365 tenant and corresponding SharePoint Online site, I've set up a PowerShell Workflow Runbook which hosts the script to configure the root site of a site.

I've imported the SharePointPnPPowerShellOnline 2.7.1609.3 modules, which allows me to use the PnP PowerShell commands.

The Apply-SPOProvisioningTemplate command doesn't seem to work correctly. I'm applying a provisioning template that I have stored inside the sharePoint site, so I'm using the following command

Apply-SPOProvisioningTemplate -Path ("https://mytenant.sharepoint.com/Sites/MySiteCollection/SiteAssets/MySiteTemplate.pnp")  

The template gets provisioned, e.g. fields, content types, lists and files are created. The script stops with the error:

Value cannot be null.
Parameter name: stream

The site pages are not deployed.

I am using parameters, but non of them is called "Stream", so I have no idea where this error comes from. Also when I use the -Handlers Files parameter to only deploy files, all files are deployed but after deployment the same error occurs.

Any ideas how to fix this issue?