Syn Error during contact Sync

[Schalex]

Hello,

I am getting always a sync error when I am syncing the contacts.
The calendar is working nicely.
But it seems that all contacts are syncing fine. When I make changes on some they are synced.

What concerns me is the following error message which I am getting always after some time of syncing.

SYNCHRONIZATION INFO
Synchronization phase: 9
Account name: Adressen (xxx@xxx.com NQ)
Authority: com.android.contacts

CURRENT REMOTE RESOURCE:
http://xxx.com:0000/carddav/......

EXCEPTION:
at.bitfire.dav4android.exception.NotFoundException: 404 Not Found
	at at.bitfire.dav4android.DavResource.checkStatus(DavResource.kt:323)
	at at.bitfire.dav4android.DavResource.checkStatus(DavResource.kt:307)
	at at.bitfire.dav4android.DavResource$processMultiStatus$3.invoke(DavResource.kt:506)
	at at.bitfire.dav4android.DavResource$processMultiStatus$4.invoke(DavResource.kt:553)
	at at.bitfire.dav4android.DavResource.processMultiStatus(DavResource.kt:567)
	at at.bitfire.dav4android.DavAddressBook.multiget(DavAddressBook.kt:127)
	at at.bitfire.davdroid.syncadapter.ContactsSyncManager.downloadRemote(ContactsSyncManager.java:338)
	at at.bitfire.davdroid.syncadapter.SyncManager.performSync(SyncManager.java:179)
	at at.bitfire.davdroid.syncadapter.ContactsSyncAdapterService$ContactsSyncAdapter.sync(ContactsSyncAdapterService.java:68)
	at at.bitfire.davdroid.syncadapter.SyncAdapterService$SyncAdapter.onPerformSync(SyncAdapterService.java:85)
	at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:272)

SOFTWARE INFORMATION
Package: at.bitfire.davdroid
Version: 1.6.3-gplay (155) Thu Jul 06 12:17:43 GMT+02:00 2017
Installed from: com.android.vending
JB Workaround installed: no

CONFIGURATION
Power saving disabled: yes
android.permission.READ_CONTACTS permission: granted
android.permission.WRITE_CONTACTS permission: granted
android.permission.READ_CALENDAR permission: granted
android.permission.WRITE_CALENDAR permission: granted
org.dmfs.permission.READ_TASKS permission: granted
org.dmfs.permission.WRITE_TASKS permission: granted
System-wide synchronization: automatically
Account: xxx@xxx.com
  Address book sync. interval: 240 min
  Calendar     sync. interval: 240 min
  OpenTasks    sync. interval: 240 min
  WiFi only: false
  [CardDAV] Contact group method: GROUP_VCARDS
  [CalDAV] Time range (past days): 90
           Manage calendar colors: true
Address book account: Adressen (xxx@xxx.com NQ)
  Main account: Account {name= XXXXXXXXX, type=bitfire.at.davdroid}
  URL: http://xxx.com:0000/......
  Sync automatically: true

SQLITE DUMP
android_metadata
	|  locale |
	|  de_DE |
----------
settings
	|  setting | value |
	|  logToExternalStorage | 1 |
----------
services
	|  _id | accountName | service | principal |
	|  3 | xxx@xxx.com | carddav | http://xxx.com:0000/acl/users/xxxx |
	|  4 | xxx@xxx.com | caldav | http://xxx.com:0000/acl/users/xxxx |
----------
sqlite_sequence
	|  name | seq |
	|  services | 4 |
	|  homesets | 4 |
	|  collections | 6 |
----------
homesets
	|  _id | serviceID | url |
	|  3 | 4 | http://xxx.com:0000/caldav/....../ |
	|  4 | 3 | http://xxx.com:0000/carddav/....../ |
----------
collections
	|  _id | serviceID | url | readOnly | displayName | description | color | timezone | supportsVEVENT | supportsVTODO | sync |
	|  4 | 4 | http://xxx.com:0000/caldav/....../Appointments/ | 0 | Termine | Alexander | <null> | <null> | 1 | 0 | 1 |
	|  5 | 3 | http://xxx.com:0000/carddav/....../Contacts/ | 0 | Adressen | <null> | <null> | <null> | <null> | <null> | 1 |
	|  6 | 3 | http://xxx.com:0000/carddav/....../Users/ | 0 | Benutzer | <null> | <null> | <null> | <null> | <null> | 0 |
----------

SYSTEM INFORMATION
Android version: 7.0 (MHA-L29C432B182)
Device: HUAWEI MHA-L29 (HWMHA)

I configured everything to a private dav server. Therefore, all the Server info is blanked with x-es and dots.
The Settings should be ok because the sync is working nicely. Only these error message is confusing me.

Can I ignore this message or is something wrong?
Thank you to everybody who takes some time to help.

Greetings Alex

[rfc2822]

@Schalex

Can I ignore this message or is something wrong?

The server has reported that a resource couldn’t be found, so synchronization is aborted.

See logs for details. This is a probably server problem.