[kronolith] Invalid byte sequence when accepting event

[lst_hoe02 at kwsoft.de]

Hello,

today we got the following error when trying to accept a invite from  
one Horde user to another :

Jul 26 16:31:47 webmail HORDE: [kronolith] SQL QUERY FAILED:  
SQLSTATE[22021]: Character not in repertoire: 7 ERROR:  invalid byte  
sequence fo                                                             
                                     r encoding "UTF8": 0xf6 0x72 0x67  
0x20
         INSERT INTO kronolith_events (event_id, event_uid, event_creator_id,
           event_title, event_description, event_location, event_timezone,
           event_url, event_private, event_status, event_attendees,
           event_resources, event_modified, event_start, event_end,  
event_allday,
           event_alarm, event_alarm_methods, event_recurtype,  
calendar_id) VALUES
           ('m3S_DfjWK-KhdFuqJQHNyCH',
            
'040000008200E00074C5B7101A82E00800000000170A59505D5FCE41AA27C7A904474
           D1B100000009378262B6DF6AC4ABEF0A516E6103476', 'xxxx',
           'Führungsrunde', '', '', NULL, '', 0, 2,
           'a:3:{s:16:"xxxx at kwsoft.de";a:3:{s:10:"attendance";i:1;s:8:"response
           ";i:1;s:4:"name";s:16:"xxxx at kwsoft.de";}s:21:"xxxx at kwsoft.de"
           ;a:3:{s:10:"attendance";i:1;s:8:"response";i:1;s:4:"name";s:16:"J▒rg
           xxxx";}s:17:"xxxx at kwsoft.de";a:3:{s:10:"attendance";i:1;s:8:
           "response";i:1;s:4:"name";s:14:"xxxx xxxx";}}', 'a:0:{}',
           1501079507, '2017-11-23 08:00:00', '2017-11-23 16:00:00',  
0, 15, 'N;',
           0, 'xxxx') [pid 32203 on line 236 of  
"/usr/share/php/Horde/Db/Adapter/Pdo/Base.php"]


For sure it looks like the display name is not properly encoded, but  
can soemone explain how to avoid this Problem. All the Horde/Kronolith  
are at latest versions and the database used ist PostgreSQL. Browser  
used from the failing Client is Chrome on Windows OS.

Thanks for any hints

Andreas