You have been right. Posteo verified that the error is caused by the broken event. After I have removed the event synchronization works now.
Thanks for your support!
I have a few calendars and contacts on an Owncloud server (https://owndrive.com/ version 8.2.2). The contacts are synchronized fine. The calendars stopped syncing a while ago. I got neither error notifications nor errors in the log file. I removed the calendar account in the DAVDroid and added it back. Now I see the calendars in the DAVDroid but not in any calendar app. I access the calendars on the Owncloud successfully with Evolution on Fedora.
note: I replaced my real username with “username” in the logs
Is there any active privacy guard etc., or have permissions been denied?
Solved! It was the MIUI (Xiaomi phones modified Android) app permission system. I’m not 100% sure, but it’s possible that this has messed up during the MIUI 7 upgrade. Few other apps were affected is a similar way.
For the reference, how to fix the problem on MIUI:
Thanks for the explanation.