Hover on the Main Menu does not work

Hi!

I have a main menu and some point of the main menu have a submenu. If I click on a submenu page and from there I hover on a main-menu point, sometimes the submenu of that page appears, sometimes not. I want that the submenu always appears.

Here is the example. When I hover on the menupoint "Chalet Kristall" the four submenu points appear "Erlebnis-Chalet", "Ausstatung", "Viedeo&Bilder" and "Familie". When I hover on "Lage & Anreise", the two menupoints "Lageplan&Google Maps" and "Tips zur Anreise" appear. Until now, everything works correct. When I click in "Tips zur Anreise" the respective page opens. This is still correct. From here, when I hover on "Chalet Kristall" again, the submenu of this main menu item "Chalet Kristall" does not appear. But if I hover on "Kulinarik" for example which is also a main menu item, its submenu appears. What is the problem? Why does the submenu of "Chalet Kristall" not appear if a subpage is active?

Thank you for your help!