It sound like you missing the files need to update from 6.1.8 to 6.1.9:
Files
application/controllers/Cron_job.php
application/controllers/Home.php
application/controllers/Messenger_bot.php
application/controllers/Payment.php
application/controllers/Stripe_action.php
application/modules/instagram_poster/controllers/Instagram_poster.php
application/helpers/my_helper.php
application/libraries/Fb_rx_login.php
application/libraries/Flow_builder.php
application/libraries/Myfatoorah.php
application/views/admin/payment/accounts.php
application/libraries/Instamojo.php
application/views
upload/ecommerce
application/controllers/Ecommerce.php
you need to copy them from the 6.2.1 package.
must go to correct folder as shown.
here is the next update from 6.2.1 to 6.2.3:
XeroChat 6.2.2 ( Change log )
(just update sql only)
Sql
UPDATE `version` SET `current`='0';
INSERT INTO version(version, current, date) VALUES ('6.2.2','1',CURRENT_TIMESTAMP) ON DUPLICATE KEY UPDATE version='6.2.2',current='1',date=CURRENT_TIMESTAMP;
Change log
- Support for flowbuilder latest update
XeroChat 6.2.3 ( Change log )
Files
application/libraries/Flow_builder.php
Sql
UPDATE `version` SET `current`='0';
INSERT INTO version(version, current, date) VALUES ('6.2.3','1',CURRENT_TIMESTAMP) ON DUPLICATE KEY UPDATE version='6.2.3',current='1',date=CURRENT_TIMESTAMP
That is all, I hope it help