The issue is related to the TXT record and only occurs when a TXT record is present.
The issue should be fixed with the next commit.
The TXT record of saldek.de seems to be wrong:
$ host -t TXT _carddavs._tcp.saldek.de
_carddavs._tcp.saldek.de descriptive text "/owncloud/remote.php/carddav/"
It should be path=/owncloud/remote.php/carddav/. However, that’s not related to the DAVdroid bug.
Until the next DAVdroid version is available, you may remove the TXT records and go with well-known paths (301 .well-known redirection).