Get an internal server error when trying to create an issue with Epic Link via REST API

Summary

The totally same symptom as JSW-13407 can be seen on JIRA Agile 6.7.14 but I'm not sure I could reopen the ticket so I create this ticket.
This problem never happened on JIRA Agile 6.7.12.

JSW-13407 has already been fixed. However, JIRA Agile 6.7.14 was released AFTER the fixed version (JIRA Software 7.1.4) had been released.

Environment

• JIRA Agile 6.7.14 (JIRA 6.4.x)

Steps to Reproduce

Please see the description in JSW-13407.

Expected Results

Please see the description in JSW-13407.

Actual Results

Please see the description in JSW-13407.

Notes

Please see my internal comment.

Workaround

Update the Epic Link Field after the ticket has been created. This can be done via REST API