Ios calendar app access no longer works after fedora upgrade

Steps to reproduce

  1. I upgraded a working owncloud carddav and caldav installation by upgrading fedora 25 to 26. IOS sync was working correctly in F25. After upgrade, I did not have access because postegres db needed upgrading manually, so I following instructions from fedora for upgrading postgres db. Then several days later (i didnt check it immediately), all my calendar events just disappeared from IOS calendar app.
  2. try to verify the ios account details for caLDAV but it will not verify them (fails) with https://myserver.com/owncloud/remote.php/dav/principles/users/myuser. Funnily enough my CardDAV still works perfectly from IOS, with bidirectional syncing. I tried all the various versions of the CalDAV address, and the only one that actually verifies in IOS is https://myserver.com/owncloud/remote.php/dav/calendars/MYUSER/personal, but even though it verifies ok, no events appear in the Calendar app in iPhone, and when I go back to CalDav account settings, it has removed the path after my server name.
    3.

Expected behaviour

calendar events should be visible in iphone and CalDav account should connect.

Actual behaviour

all calendar events disappear

Server configuration

Operating system: Fedora 26 amd64

Web server: nginx 1.10.3

Database: postgres 9.6.3

PHP version: php-fpm 7.1.6

ownCloud version: (see ownCloud admin page) 9.1.5

Updated from an older ownCloud or fresh install: updated as part of fedora upgrade?

Where did you install ownCloud from: fedora repos

Signing status (ownCloud 9.0 and above):

Login as admin user into your ownCloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results into https://gist.github.com/ and puth the link here.

says 404 not found

The content of config/config.php:

Log in to the web-UI with an administrator account and click on
'admin' -> 'Generate Config Report' -> 'Download ownCloud config report'
This report includes the config.php settings, the list of activated apps
and other details in a well sanitized form.


or 

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your ownCloud installation folder

*ATTENTION:* Do not post your config.php file in public as is. Please use one of the above
methods whenever possible. Both, the generated reports from the web-ui and from occ config:list
consistently remove sensitive data. You still may want to review the report before sending.
If done manually then it is critical for your own privacy to dilligently
remove *all* host names, passwords, usernames, salts and other credentials before posting.
You should assume that attackers find such information and will use them against your systems.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your ownCloud installation folder.

Are you using external storage, if yes which one: local/smb/sftp/... NO

Are you using encryption: yes/no NO

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/... NO

LDAP configuration (delete this part if not used)

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your ownCloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser: firefox 51

Operating system:

Logs

Web server error log

Insert your webserver log here

ownCloud log (data/owncloud.log)

Insert your ownCloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 
c) ...