It was working flawlessly until the owncloud upgrade to the latest stable version (on debian) version 9.1.3-1.1. Before that I used Owncloud 8.2 without any problems.
Here is the problem:
If I (owncloud user 1) create an new calendar and share it (with the permission to change entries), I could create calendar entries. I also could create entries to my own non-shared calendar too. But I could not add an entry in a calendar which is shared for me (by the owncloud user 2) - an that’s the problem. I also could not change exsiting entries in the shared calendar.
Used Davdroid-versions: one device (Redmi Note 2 MIUI 7) with the actual google play store version (188.8.131.52-gplay), this device is used by owncloud user 1. The other one (Samsung S7 actual stock ROM) with the latest F-droid version (1.3.6-ose), this is used by owncloud user 2.
The problem seems independent from the device or the owncloud user. If I create a calendar on the Redmi and share it, the S7 could not change anything on the shared calendar and vice versa. I also restarted both devices and reinstalled their DAVDROID-versions.
DAVDROID itself recognises the problem. After saving the entry, it lasts a minute or two until I get a notification that “Kalender-Synchronisierung fehlgeschlagen - Serverfehler beim Hochladen neuer/geänderter Einträge”
could be translated to: ‘calendar synchronisation failed - server errror while uploading new/changed entries’
To eliminate an Owncloud problem I did the following: I (as owncloud user 1) used Thunderbird and added the own and shared calendars and tried to add entries and to change entries on the shared calendar - no problem.
debug log: 0_1484165442856_debug_Redmi.txt