Disappearing main menu - Users with multiple inboxes / mail accounts

When I go to Email and select a different inbox from the default one (for users with multiple inboxes), the main menu disappears. Anyone got a similar problem? Fix? Thanks.

Steps to reproduce:

  1. Select “Emails” on the main menu.
  2. Click on the grey INBOX button on the right.
  3. Click on an inbox in the pop-up window.
  4. You get a page with the title “Emails” showing the chosen inbox but no main menu at the top of the page.

Version: 8.1.2