Get original post ID after wp_insert_post

I have a plugin with several CPTs (we’ll call them CPT-A, CPT-B, CPT-C, and CPT-D). All CPTs have custom fields. In CPT-D, the user is able to make a selection and assign a post in CPT-A, CPT-B, and CPT-C to the current post in CPT-D. Basically linking relevant records to each other.

If the post in CPT-A, CPT-B, and/or CPT-C does not yet exist, the user can “quickly” create the post by entering the post’s title using a standard text input field. No other data is required, and any optional data can be entered later.

I then will use wp_insert_post() to add the new post (CPT-A, CPT-B, and/or CPT-C). This all works as expected.

Next, I need to update CPT-D’s postmeta with the post ID of the new CPT-A, CPT-B, and/or CPT-C. To do this, I am using update_post_meta().

The problem I’m having is that the wrong post’s postmeta is being updated.

For example, if CPT-D’s Post ID is 99, it should have postmeta meta_key ‘assigned-cpt-a’ = 100, ‘assigned-cpt-b’ = 101, and ‘assigned-cpt-c’ = 102 if all three CPT’s are set.

What happens instead is:
CPT-D gets postmeta ‘assigned-cpt-a’ = 100
CPT-A gets postmeta ‘assigned-cpt-b’ = 101
CPT-B gets postmeta ‘assigned-cpt-c’ = 102

Here is a sample of the code that inserts the new CPT and updates postmeta:

<?php
$new_cpta_title = sanitize_text_field( $_POST[ 'cpt-a-name' ] );
/* Only add new if a CPT with the same title doesn't already exist */
if( null == get_page_by_title( $new_cpta_title, OBJECT, 'cpt-a' ) ) {
    $new_cpta_slug = preg_replace("/[^A-Za-z0-9]/",'',strtolower($new_cpta_title));
    $author_id = get_current_user_id();
    $new_cpta = array(
        'comment_status'    =>  'closed',
        'ping_status'       =>  'closed',
        'post_author'       =>  $author_id,
        'post_name'         =>  $new_cpta_slug,
        'post_title'        =>  $new_cpta_title,
        'post_status'       =>  'publish',
        'post_type'         =>  'cpt-a'
    );
    wp_insert_post( $new_cpta );

    $new_cpta_info = get_page_by_path($new_cpta_slug, OBJECT, 'cpt-a');
    if ( $new_cpta_info ) {
        $new_cpta_ID = $new_cpta_info->ID;
        update_post_meta( $post_id, 'cpt-a-id', $new_cpta_ID );
    }
}

So, my question is, how can I reset the $post_id in update_post_meta to be the same post ID as the original CPT-D?