Summary
If you press F5 or Refresh the web page, the Navigation buttons in the entity details will disappear.
Question
If you open Entity Details from Grid View, there are Navigation buttons which allow you to move to the Previous and Next Entity. In case that you press F5 or Refresh the web page, those buttons dissapear.
Answer
This is an expected behavior and by design. Reason being that the navigation button is based-on a grid in the background. After reloading, we lose the context of the background grid, so we don't know the previous one or next one.