i made this experiment

i add an event in the smartphone calendar
then
i ask for memotoo to sync but it fails

all the events contained in the calendar was send instead of the sole new one
pc calendar is not updated with the new event

server says :

calendar: starting slow sync, two-way (peer is client)
creating complete data backup of source calendar before sync (enabled with
dumpData and needed for printChanges)

*** calendar ***
Comparison was impossible

calendar: started
calendar: received 16
calendar: slow sync done unsuccessfully

local, status 10400

Synchronization failed, see
/home/roubach/.cache/syncevolution/kontact-2014-01-15-18-06/syncevolution-log.html
for details.

calendar |  1  |  0  |  0  |  0  |  0  |  0  |  0  |  0  |  0  |
|      slow, 0 KB sent by client, 8 KB received                       |
|      15 item(s) matched                                             |
|      item(s) in database backup: 15 before sync, 16 after it        |
|      local, status 10400                                    

 start mer. 15 janv. 2014 18:06:41 CET, duration 0:05min       |
|            incomplete sync session (local, status 20023)      

First ERROR encountered: local, status 10400

[INFO] sync: /org/syncevolution/Session/18425227001389805601: 
Data modified locally during synchronization:

[INFO] sync: /org/syncevolution/Session/18425227001389805601: *** calendar ***
[INFO] sync: /org/syncevolution/Session/18425227001389805601: no changes

see kontact-2014-01-15-18-06_syncevolution-log.html