Article Preview in admin panel?

If I edit any of my articles in admin (0.6.0) and I want to preview it using preview button I get the message:
"Template default.html.twig is not defined"
My standard template is Agency which is set so in admin config.
In my local setup I get: the message: “Not Found”

Message in Terminal in local installation is:
/admin/media/home/_bilder.json/task:listmedia - No such file or directory
/admin/media/home/_bilder.json/task:processmarkdown - No such file or directory

Just tested another skeleton/template (woo). Same message in preview of modular pages:
“Template default.html.twig is not defined”
Style Guide site (non modular) preview works.

Is this issue the same as this one in github?

I think it is… Can we take the issue there? Easier to track that way.