Can’t find WordPress should correct invalidly nested XHTML automatically

Hi,

My client is using a custom-developed theme. I used Elementor to add new pages into the website, I only added text and images and suddenly, the chinese version of the website has all texts in Italic while the English version remained normal.

I tried looking for the “WordPress should correct invalidly nested XHTML automatically option” in the Settings->Writing tab but this setting does not exist here.

How can I fix this?