Inline issue create fails to attach to Epic when there are multiple custom fields with the name "Epic Link" or "Epic link"

Summary

There is a bug in the inline issue create where there are multiple custom fields with the name "Epic Link" or "Epic link" in the database. There will also be a duplicate custom field in one of the projects.

You can replicate that by creating a custom field named as Epic Link under a Team-managed project.
 

Steps to Reproduce

1. Open a Scrum board that meets the above conditions https://<instance>.atlassian.net/secure/RapidBoard.jspa?rapidView=xxx&view=xxxx.xxxx&epics=visible 
2. Select an Epic from the Epic panel
3. Click on + Create issue to create a new issue
4. Expect the issue to be created as part of the EPIC but instead get created with pop up 'Your issue xxxx has been created but is not currently visible."
5. Instead the issue appears at "Issues without epics" but can be moved easily to the EPIC after creation

Expected Results

Issue will be created and added to the Epic

Actual Results

Issue will be created but not added to the selected Epic. 

Workaround

You can move the created Issue to the EPIC after creation manually. Or you can also rename the custom field(s) whose name is Epic Link to something else.