Single page multiple categories

Hello,
I am using Accesspress as a parent theme and I am mostly happy with it.
I already posted my issue in the theme’s support page and didn’t get any answer. I don’t think this issue is limited to the theme though.
Here is the problem I am facing:
As theme instruction to create a blog, I created a category called blog and assigned posts that need to be shown there. I have a nav in the menu for it.
My client likes to have some of these posts also assigned to another category called Podcast which also has a nav in the menu. So far, so good, the problem accords when user click on the (..more) link and the whole post appears with both nav highlighted on top menu: https://training.bhhscalifornia.com/greggneuman/

I tried few solutions I found online, but it didn’t work. such as
//custome post template for podcast
function get_custom_cat_template($single_template) {
global $post;

if ( in_category( ‘podcast’ )) {
$single_template = dirname( __FILE__ ) . ‘/single-template.php’;
}
return $single_template;
}

add_filter( “single_template”, “get_custom_cat_template” );

by using above code both blog and podcast are using single-template.php
Would you please help me with this problem

I really appreciate your help in advance.