I came across an interesting situation at a client when trying to deploy an ARM template that I have deployed a few times in the past successfully on both Azure and Azure Stack.  What the template deploys does'nt matter, but I came across a problem that you might encounter when deploying a Template with parameters, more specifically, how they're named.

I tried to deploy a template I modified back in January to a customer's Azure Stack stamp that was at the latest update version (1905) at the time of writing. 

The parameters looked like this:

When I tried to do a custom deployment, I got the following:

I tried to deploy the same template to Azure and it worked, so I knew the template was OK.  I also tried on a 1902 system and it worked.  Testing on a 1903 system and I got the error above again, so whatever change is causing the problem was introduced with that update and continues onwards.

After some trial and error,  doing a find/replace renaming the parameter to remove the '_' before the _artifactslocation &  _artifactsLocationSasToken in my templates. It wasn’t so obvious from the error message what the issue was, one of the joys of working with ARM!

Hopefully this issue gets fixed as _artifactsLocation and _artifactsLocationSasToken are classed as standard parameters per https://github.com/Azure/azure-quickstart-templates/blob/master/1-CONTRIBUTION-GUIDE/best-practices.md