Taxonomy terms disappearing I'm working with Drupal 8 Taxonomy terms. I'm managing them in the backend through the default taxonomy pages.

I'm doing this for a project where I need to label rows in a custom added table. 

This all worked pretty fine until suddenly, just out of nowhere, the terms disappeared. I added terms, and when I returned to the list page of the specific taxonomy library, they where gone. They were still in the database, and \Drupal\taxonomy\Entity\Term::loadMultiple() still returns them.

I've done a lot of digging, but I'm out of ideas. I need some pointers to continue my search.
I found the issue. The taxonomy terms where stored without the taxonomy_term_hierarchy information. This info is needed for the list of terms in the admin list to determ the relations between the terms.

This was caused by me, I've removed the hierarchy field from the form. This caused Drupal to not save this information at all. There are no default values or something like that here.

https://www.drupal.org/files/drupal7-db-schema.png