Boards not always deleting with project deletion

Summary

While deleting a next-gen project, the board related to that project is not always deleted with it. This problem is intermittent but the board cannot be deleted from the UI.

Environment

Jira Software Next-Gen projects.

Steps to reproduce

1. Delete a next-gen project.

Expected results

All project dependencies should be deleted along with the project.

Actual result

The board related to the project still showing on the board page and cannot be deleted.

Workaround

Create a support ticket at http://support.atlassian.com.