I see the following errors in /var/log/roundcube/errors:
[07-Oct-2019 21:38:14 Europe/Berlin] PHP Parse error: syntax error, unexpected ')' in /usr/share/roundcubemail/plugins/calendar/drivers/database/database_driver.php on line 1127 [08-Oct-2019 16:22:54 Europe/Berlin] PHP Parse error: syntax error, unexpected ')' in /usr/share/roundcubemail/plugins/calendar/drivers/database/database_driver.php on line 1285
I guess we need to remove the "," here:
. $sql_add,