Can not delete any files

Hi community!

I’m using nc 18.0.3 and cannot delete any files.
This is what i get in the log:

Sabre\DAV\Exception\Forbidden:

  1. /var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Tree.php - line 179:OCA\DAV\Connector\Sabre\Directory->delete()
  2. /var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 287:Sabre\DAV\Tree->delete()
  3. <>Sabre\DAV\CorePlugin->httpDelete()
  4. /var/www/html/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105:call_user_func_array()
  5. /var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479:Sabre\Event\EventEmitter->emit()
  6. /var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254:Sabre\DAV\Server->invokeMethod()
  7. /var/www/html/nextcloud/apps/dav/lib/Server.php - line 319:Sabre\DAV\Server->exec()
  8. /var/www/html/nextcloud/apps/dav/appinfo/v2/remote.php - line 35:OCA\DAV\Server->exec()
  9. /var/www/html/nextcloud/remote.php - line 165:require_once("/var/www/ht … p")

I can create new files and rename…

The files are stored on SMB (external_files / external Win Server 2012)
PHP Version: v7.4.4
Ubuntu: Focal Fossa / full patched

Can anybody help me?