Use separate base CDN URLs when using Statically.io with Autoptimize on child sites.
Snippet Type
Execute on Child Sites
Snippet
add_filter( 'autoptimize_filter_cssjs_multidomain', function(){
return array( 'https://cdn.statically.io/js/example.com', 'https://cdn.statically.io/css/example.com' );
} );