Selected document not be added to metadata when creating a manual assignment

Hi all, 

I've got a customer with a unique issue similar to the problem outlined in the link below. 

When logged in as an administrator, right clicking an existing document > Create > Assignment doesn't add the property 'Document' with the link to the document object to the Assignment metadata card. 
There isn't anything in the metadata card configuration and nothing is set under the visible property settings. It works when using a workflow which makes me think permissions but I'm not sure which ones specifically could cause it. 

community.m-files.com/.../27618