Owncloud contacts disappeared on server, not on PC

Steps to reproduce
1. open contacts app on server via browser

Expected behaviour
All available contacts should be visible.

Actual behaviour
Only contacts in groups are visible, all other contacts (not grouped) have disappeared. In Thunderbird and Android, they are still there.

Server configuration
Operating system: shared hosting
Web server:
Database: mysql
PHP version:
ownCloud version (see ownCloud admin page): 9.0.1
Updated from an older ownCloud or fresh install: updated regularly
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):

ownCloud log (data/owncloud.log)

Sorry, don't know what to look for...

Integrity status for oC9+

No errors have been found.

from the issue template you have filled out:

Before posting please snip make sure that you're running the latest available version for your oC release: https://owncloud.org/changelog/

9.0.1 is way too outdated to report issues here.