This is not related to updating Android. Please follow up at https://forums.bitfire.at/topic/1259/rev-must-not-appear-more-than-once-in-a-vcard-component/
I installed Owncloud 9.0.2 with MariaDB and NginX on Ubuntu 16.04 in a virtual Machine (Server2012 R2)
For the installation i used this MANUAL and I did it exactly like described. (Except IP´s and the Domain)
On my cell phone´s I have the newest version of Davdroid (1.08)
To Sync calDAV and cardDAV with my Owncloud I use ClDav Synchroniser, and it works very fine.
So, but when I try to sync my Owncloud with Davdroid he tells me, he´s not able to find a calendar.
I tried following links in Davdroid (with internal and external address):
https:// 10.0.XX.XX/owncloud/remote.php/dav/ https:// 10.0.XX.XX /owncloud/remote.php/dav/principals/Bernd https:// 10.0.XX.XX /owncloud/remote.php/dav/principals/ https:// 10.0.XX.XX /owncloud/remote.php/ https:// 10.0.XX.XX /owncloud/ https:// 10.0.XX.XX/owncloud/remote.php/dav/principals/users/Bernd/ https:// 10.0.XX.XX/owncloud/remote.php/dav/principals/users/ https:// 10.0.XX.XX/owncloud/remote.php/dav/principals/calendars/ https:// 10.0.XX.XX/owncloud/remote.php/dav/principals/calendars/Bernd
I also tried to disable the http2 in my configuration.
With and without präaptive autentification.
Different cell phones (all Android and newest version of Davdroid)
Attached a bug report from my cell phone.
Actually Davdroid works very well with my actually Owncloud 8.2.3 installation, described HERE
I would be very happy if we can solve this problem (This is the last point on my checklist to go live with my OC9 installation)
PS: sorry for my horrible English
According to the logs:
EXCEPTION java.io.IOException: stream was reset: REFUSED_STREAM
this is a duplicate of nginx HTTP/2 incompatible with okhttp. Please follow up there.