Horde/Turba contact photos not synced

[thomas1981]

About my environment:
Horde 3.3.6 (stable), Turba 2.3.3, running with https
Samsung OmniaLite GT-B7300, Windows Mobile 6.5, Synthesis SyncML Client STD 3.0.2.24

Basically syncing contact works fine in both directions. Contact photos get synced from the phone to Turba, but unfortunately they won't get synced back when modifying contacts in Turba. The result is, that contact photos are deleted on the phone and remain in Turba, regardless of any further syncs.

According to the Horde log files, Turba sends the image back. /tmp/sync/data.txt lists the photo data in both sections "received from backend" and "converted for client":
BEGIN:VCARD
VERSION:2.1
NICKNAME:
BDAY:
PHOTO;ENCODING=b;TYPE=JPEG:w7/DmMO/w6AAEEpGSUYAAQEBAHoAegAAw7/DmwBDAAg...

/tmp/sync/log.txt show nothing out of the ordinary:
DEBUG: Sending 1 server changes for client URI contacts
DEBUG: Sending replace from server: 20100221132611.33961m958i82mulc@mydomain.com
DEBUG: Sending <Final> to client
DEBUG: Return message completed

I already talked to the Horde developers, who think it's a
client issue. They asked me to verify that the PHOTO attribute looks the same in both sync directions? How can I figure this out in the Synthesis client?

Anyone experiencing a similar problem? Is this a problem within the Synthesis client or possibly of Windows Mobile Outlook? Any solutions?

Thanks in advance, Tom