One more thing I found out:
our original X-Store Child Theme had this function in functions.php:
//Remove Query Strings From Static Resources
function smartwp_remove_query_strings_from_static_resources( $src ) {
if( strpos( $src, '?v=' ) ){
$src = remove_query_arg( 'v', $src );
}
if( strpos( $src, '?ver=' ) ){
$src = remove_query_arg( 'ver', $src );
}
return $src;
}
add_filter( 'script_loader_src', 'smartwp_remove_query_strings_from_static_resources', 999 );
add_filter( 'style_loader_src', 'smartwp_remove_query_strings_from_static_resources', 999 );
// Add mailchimp integration
add_action('wp_head', function() {
?>
<script id="mcjs">!function(c,h,i,m,p){m=c.createElement(h),p=c.getElementsByTagName(h)[0],m.async=1,m.src=i,p.parentNode.insertBefore(m,p)}(document,"script","https://chimpstatic.com/mcjs-connected/js/users/ba7e51eafdcb61b2943699529/cbf3f511c5104a42d1d457e3e.js");</script>
<?php
});
Which also causes the same issue.
When removed from functions.php, and your Remove Query Strings From Theme Static Resources is turned on, the same issue.
Basically, your theme or jscomposer doesn’t like query strings removed for some reason.