Button "Relate existing entity to group" redirects to wrong page

Problem/Motivation

I cannot add or relate existing content to my group. I've set up a test site with not much content in it other than a group type, a group and a basic page.
When under the "Related entities" tab, the "+ Relate existing entity to group" button point to /group/2/content/add . However, when i follow the link, it redirects me to /group/2/content/add/group_membership , which shows a page to add members.

Proposed resolution

Link the "+ Relate existing entity to group" button to a page that allows me to relate an existing entity to groups.