White space on the right on mobile

add the following under CSS in advanced options

html,
body{
width:100%;
overflow-x:hidden;
}

Tried to add the code at the custom page CSS but doesn’t seem to work…

interesting. You need to do it for each page. The problem you’re having is like this https://imgur.com/a/25cixgK ?

@chris100184 Yepp, like that

And you’ve done the following https://ibb.co/tDsH6hM ?

Can you please provide the url ?
I can take a look at it.

Check the padding and/or distance of elements from your sections. One of it could be “off canvas”. – (minus) on right will push the element out of viewport.