Can you retry to create the account, while running the messageserver in debug mode ?
[defaultuser@Sailfish ~]$ systemctl --user stop messageserver5
[defaultuser@Sailfish ~]$ devel-su -p
[defaultuser@Sailfish ~]$ QT_LOGGING_RULES="*.debug=true" messageserver5
It seems that the message server is failing and restarted by systemd from your logs.
After you get the debug log, you can start it again in normal mode with:
[defaultuser@Sailfish ~]$ systemctl --user start messageserver5