[Posteo] Server didn't provide ETag

[zWhdmB5T]

Problem scope

• I'm sure that this is a DAVx⁵ problem.

App version

• I'm using the latest available DAVx⁵ version.

Android version and device/firmware type

Samsung Galaxy Tab A8 SM-X200 X200XXS6DYG6/X200OXM6DYG6 Android 14

Steps to reproduce

System with Issue

• Samsung Galaxy Tab A8 SM-X200 X200XXS6DYG6/X200OXM6DYG6 Android 14
• DAVx⁵ 4.5.3-ose (F-Droid)
• Posteo: CalDAV and CardDAV (account x)
• error message "HTTP-Serverfehler - Server didn't provide ETag"

System without Issue

• Google Pixel 6a bluejy-16.5-13291547 2025090300 Android 16
• DAVx⁵ 4.5.3-ose (F-Droid)
• Posteo: CalDAV and CardDAV (account y — different to account x)
• no such error message

Further info

• DAVx⁵ is configured equally on both devices

debug-info.txt
logcat.txt

[rfc2822]

Tried with our Posteo test account and couldn't reproduce the problem.

The part of the logs look like a server problem:

09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: Caused by: net.fortuna.ical4j.data.ParserException: Error at line 1:Expected [BEGIN], read [��8묥�&�Qk6���#�]
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.assertToken(SourceFile:16)
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.parseCalendarList(SourceFile:8)
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.parse(SourceFile:13)
...
09-06 08:42:41.903 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data
09-06 08:42:41.904 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data
09-06 08:42:41.906 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data

The responses look invalid and empty. There are neither event data nor an ETag.

I doubt it's a DAVx5 problem.

Does it happen for every sync on your affected device or only at certain times?

Does it happen when you only sync another, empty calendar, on the affected device?

Can you provide the debug info of the specific error (tap the DAVx5 error notification and then share)?