Sidemenu - new page has no back button

I have a side menu on page A which links to a page B. Page B shall not have a side menu and be rather “on top” of the current page. There should be a back button which goes back to Page A.

What currently happens:
If I click the ion-item link to page B, it opens but has no back button shown, although it has a nav bar with ion-nav-back-button.

I have no menu-close defined on the ion-item within the sidemenu.

Any idea how to get this working?