Issues are no longer visible when moving issues to back to `Backlog` from assignee list on issue board

Summary

Issues sometimes disappear from the view when moved back to the backlog.

Steps to reproduce

  1. Create a new project.
  2. Create a new issue board.
  3. Add an assignee list to the issue board
  4. Add a new issue to the backlog.
  5. Move the issue to the assignee. The number of issues for the Backlog column remains at 1.
  6. Move the issue back to the backlog. The issue will disappear, but the totals for the columns will be correct: 1 for Backlog, 0 for the assignee.
  7. Refresh the page to see the issue in Backlog.

Example Project

https://gitlab.com/asaba/issue-board-bug/boards?scope=all&utf8=%E2%9C%93&state=opened

What is the current bug behavior?

The issue disappears from view when moved to the Backlog.

What is the expected correct behavior?

The issue should be visible in the Backlog as soon at it is moved.

Relevant logs and/or screenshots

Boards___Antony_Saba___issue-board-bug___GitLab

Boards___Antony_Saba___issue-board-bug___GitLab

Boards___Antony_Saba___issue-board-bug___GitLab

Output of checks

This bug happens on GitLab.com.

Possible fixes