Editing any Sub-Tasks would replace the Description Field.
- Open Sub-Task administration (/secure/admin/subtasks/ManageSubTasks.jspa)
- Use Edit operation (secure/admin/subtasks/EditSubTaskIssueTypes!default.jspa)
- Check the Description field.
The Description field should be maintained to the value it was before the edit button was clicked.
The Description field is replaced automatically by JIRA with the name of the sub-task
Tested in FF 39, Chrome 44