SuiteCRM - email templates not working

I am unable to use email templates on Suitecrm. See attached screenshot of the error.
ERROR CONNECTING to: ./index.php?entryPoint=json_server, ERROR:SyntaxError: Unexpected token B in JSON at position 0

On my production site I’m currently using version 7.3.1

I tried new version 7.8.2 on localhost, but it still produce the same error.

I also found the solution from github, it needs to update code outside custom folder. here’s the solution: (problem) (update code)

I tried that solution on crm localhost and works.

But I wonder why that’s not applied to the latest crm version?
If I change the code, is that safe for my production site?


Do you have any better idea on how I can fix this?

Thank you.

,also on the demo site, why there’s no error there? I can use email template.
is there any configuration server need to do?

Thank you.

I got the solution,

so the problem is on our php configuration. we need to enable mbstring.encoding_translation value to “on” in php.ini . since we use ubuntu with php 5.6, so the php.ini file for apache web server could be found in /etc/php/5.6/apache2/php.ini (sometimes).
with this change on php configuration we don’t need to update suitecrm core.

my reference :