Troubleshooting a custom template failing to generate

[ransagy]

We have a template package that contains 3-4 Project templates.
Lately, One of them stopped working and fails generating with the following error, even with the dotnet CLI contet env var enabled, --debug:reinit/--debug:customhive, verbosity set to diag, etc.

Template "MY_TEMPLATE_NAME_HERE" could not be created.
      Failed to create template.
      Details: Error while processing file /content/MyTemplateProject/Program.cs
      Object must implement IConvertible.

The authoring CLI tool's Verify command gives the same.

Any idea how i am supposed to further troubleshoot it?