Quick actions are broken in epics

Summary

Quick actions in comments or descriptions are not working anymore in epics (gitlab.com)

Steps to reproduce

Go to an epic page, like &243
Try to use a quick action (ex: /label)

What is the current bug behavior?

Loading permanently, and actions are not applied.

What is the expected correct behavior?

Autocompletion of action or content.
Actions performed

Relevant logs and/or screenshots