PenciDesign replied
Hi,
No - It's not all plugins you're using. You're using more plugins inside wp-content/plugins/mu-plugins.
Also, I don't know what's the codes you've modified via child theme.
So, I recommend you tried a fresh install WordPress with latest version of this theme and check if this issues is appears or not ( of course please check on different hosting or different domain ).
If this issue doesn't appears, that mean you've did something wrong on the child theme to caused this issue or you're using a plugin caused it doesn't work.
We can't check it helps you because we can't access to the files on your hosting..
Best Regards,
PenciDesign