Issue

Currently, the "Parent Link" field is NOT cleared for an issue when it is moved from hierarchy at Epic Level or above to Story level.

For example, the project hierarchy is Initiative -> Epic -> Story -> Sub-Task

I have an Epic with "Parent Link" set to an Initiative. At a later date, after backlog grooming, I move the Epic to a Story and set a Epic Link. The Parent Link is not available on UI now, even though the value is NOT cleared.

Now, when I remove the Epic Link I set, the Parent Link is displayed as shown below, which is incorrect. This incorrect setting of Parent Link is creating problems with the JQL queries we run and also the boards we have configured in our projects.

Workaround

Create an automation rule that will automatically clear the Parent Link field whenever an issue is moved to a new issue type, as explained in the KB article linked below:
https://confluence.atlassian.com/automationkb/automation-for-jira-how-to-clear-the-parent-link-field-when-an-issue-is-moved-to-a-new-type-1206795140.html