I am using a next gen project and have encountered a strange scenario whereby:
- I add child stories to an Epic
- When I go to the backlog some epic link labels are visible against their stories and others are not (see picture)
Some extra information:
- It seems either all stories within an epic are effected and do not display the epic link label or all stories within the epic are fine.
- I added an "At Risk" status to my board which some stories and Epics sit in.

Let me provide further examples:
1. I created a new epic and added a story as you can see it displays correctly:

2. Then I update the Epic Name to "XXXX" and it disappears:

3. Then once more I update the Epic Name with some special characters "%$$ 123 ABCDEFG" and it reappears.

4. Finally I remove the special characters and it once more disappears!

WEIRD!