[sync] DAV issue - base uri

[T. Welz]

Hello,

I want to sync contacts/calendars with android. I tried different 
android apps, until I figured out that already connecting to the 
principals URL is failing.

When I access the principals url 
https://www.XXXXXX.eu/horde/rpc.php/principals/tw/ with a webbrowswer 
manually I get:

<d:error><s:exception>Sabre\DAV\Exception\Forbidden</s:exception><s:message>Requested 
uri (/horde/rpc.php/principals/tw/) is out of base uri 
(https://www.XXXXXX.eu/horde/rpc.php/)</s:message><s:sabredav-version>1.8.10</s:sabredav-version></d:error>

I tried to access the principals url with the demo of horde, there i can 
access the url without error - so I assume the issue is the base uri.

I tried to find a spot in the configuration where to set the base uri - 
but i couldn't.
Does one of you can give me a hint were to set this, please. Or am I on 
a wrong path, and connection issue is something different.

Versions:
Horde Groupware 5.2.2
Kalender (kronolith) 
<https://www.wiznet.eu/horde/admin/config/config.php?app=kronolith> 4.2.2
Adressbuch (turba) 
<https://www.wiznet.eu/horde/admin/config/config.php?app=turba> 4.2.2
Webmail (imp) 
<https://www.wiznet.eu/horde/admin/config/config.php?app=imp> 6.2.2
Server is Debian Stable.


Regards Tobias