Unable to add related issues if they came from a different project

Summary

Currently it is not possible to link related issues from differnt projects which is very disruptive since our software is located in a lot different projects. (framework, plugins main app)

https://twitter.com/gitlab/status/1108198746498744320

Steps to reproduce

• all projects are owned by the same group
• try to add a related issue from a differnt project
• the issues will not ne suggested and if the name is manually added the add button is grayed out

Frequency

• Always

What is the current bug behavior?

• unable to link related issues from a different project

What is the expected correct behavior?

• the issues from differnt projects should be added
  (since this also already work in commit messages and other places)

Gitlab Info

Self hosted - Gitlab - EE Starter
GitLab 11.9.1-ee (b50dc44d)
GitLab Shell 8.7.1
GitLab Workhorse v8.3.1
GitLab API v4
Ruby 2.5.3p105
Rails 5.0.7.1
postgresql 9.6.11