only unwatched movies displayed

I experience a funny behavior: only unwatched movies a shown

* The database consists of app 1000 movies, with about 25 of them unwatched.
* It shows e.g. all the actors, but only those appearing in the 20 unwatched movies show when selected
* Similar with years etc
* The moment it’s marked as watched, it ‘disappears’ from the display and even from the Video-Source
* TV-Shows behave as expected

There seems to be some filter, but where and how to reset ?
Thank you for your help!

Kodi: 18 Alpha
Skin: Estuary
OS: Ubuntu 16.04