Contacts doesn't load

Server
, ,
1

Actual behaviour
1. go to "contacts"
2.waiting... I only see the animated "wait icon" in the middle

Yesterday I starts to use the contacts in oc. First I created a test contact. Then I imported some contacts. All works fine. I can see all contects, can edit etc.
Also webDAV sync with android work fine.
But 2016-08-08, I dont see any contacts in browser desktop. To "waiting" icon runns for minutes (and maybe hours) without any activity.
Can you help me to reproduce whats going wrong?
thanks.

Server configuration
Operating system: linux
Web server: apache2
Database: mysql
PHP version: 5.6.21
ownCloud version: ownCloud 9.0.2 (production)
Updated from an older ownCloud or fresh install: 8.0 > 9.0 some weeks before
Special configuration: no

Integrity status for oC9+

Login as admin user into your ownCloud and access
http://example.com/index.php/settings/integrity/failed
"Integrity checker has been disabled. Integrity cannot be verified."
not sure where I can activated this feature.
2

Probably:

Also consider to update to the latest available 9.0.4 before reporting any issues with outdated oC version like 9.0.2

3

Now I upgraded oc to 9.1.0 and the app contacts to 1.3.1.0
But the issue still exist.

after upgrade I got an additional error with the app "bookmarks":
"Call to undefined method OC_L10N::get() at /owncloud/apps/bookmarks/appinfo/app.php#31" during activation.

4

Well, the issue linked above is still open and not marked as fixed.

5

I think it's a problem with the contacts.
I deleted all rows in oc_cards and oc_cards_properties exclude "addressbookid = 1" and now the contacts site worked. But without my previous data.