It was already reported in a couple of places and different client software:

• EmCLient: https://issues.kolab.org/show_bug.cgi?id=5427
• DavDroid: https://forums.bitfire.at/topic/1360/kolabnow-sync-fails-when-changing-notes-field/2

According to DavDroid devs it is not required by standards. So, we should investigate that.

Current code in Kolab/CardDAV/ContactsBackend.php (and CalendarBackend.php) is:

// sanity check
if ($object['uid'] != $uid) {
    rcube::raise_error(array(
        'code' => 600, 'type' => 'php',
        'file' => __FILE__, 'line' => __LINE__,
        'message' => "Error creating contact object: UID doesn't match object URI"),
        true, false);

    throw new DAV\Exception\NotFound("UID doesn't match object URI");
}

we should test what happens if we just replace this code block with:

$uid = $object['uid'];

Maybe we'd need to check if uid is not empty and store the original URI in some custom X-property or sth.