I haven't been able to reproduce this, but there are enough independent reports that this almost certainly a real issue, or a vast conspiracy:
- See PHI668.
=== Steps to reproduce:
1. Create a new project.
1. Create the workboard for the new project.
1. Change the default workboard filter (it has to be a custom query rather than one of the built-in ones, I changed it to tasks assigned to myself).
1. On the “backlog” column, click “View as Query”.
1. Click “Search”.
1. Go back to workboard page, get 404ed.