I use ACF.

I have the following code:

$args = array(
    "post_type"         => "membership",
    "posts_per_page"    => 1,
    'meta_query'        => array(
        'relation'      => 'AND',
        array(
            'key'       => 'kennel',
            'value'     => '"' . $toReturn["request"]["groupId"] . '"',
            'compare'   => "LIKE"
        ),
        array(
            'key'       => 'user',
            'value'     => $toReturn["userId"],
            'compare'   => "="
        )
    )
);

$the_query = new WP_Query( $args );

if ( $the_query->have_posts() ) {

    while ( $the_query->have_posts() ) {
        $the_query->the_post();
        $mid = get_the_ID();

        $totalRuns = uc_totalRuns($mid);
        $unprocessedRuns = uc_unprocessedRuns($toReturn["request"]["groupId"], $toReturn["userId"], "registered"); // <!-- Changes get_the_ID()

        if ($totalRuns == 0 && $unprocessedRuns["unprocessed"] == 0) {
            wp_delete_post( $mid );

            $toReturn["success"] = true;


        }
    } 
}

wp_reset_postdata()

After calling uc_unprocessedRuns(), the value that is returned by get_the_ID() is different.

This is uc_unprocessedRuns():

function uc_unprocessedRuns($groupId, $memberId, $type) {
    $toReturn["unprocessed"] = 0;

    //Get unprocessed runs
    //This call returns a post with the ID that is later returned by get_the_ID() in the calling code.
    $args = array(
        "post_type"         => "run",
        'posts_per_page'    => -1,
        "meta_query"        => array(
            'relation'  => 'AND',
            array(
                'key'       => 'kennel',
                'value'     => '"' . $groupId . '"',
                'compare'   => "LIKE"
            ),
            array(
                'key'       => 'processed',
                'value'     => 0,
                'compare'   => "="
            ),
        )
    );

    $the_query = new WP_Query( $args );

    $runIds = array();
    if ( $the_query->have_posts() ) {
        while ( $the_query->have_posts() ) {
            $the_query->the_post();

            $runIds[] = get_the_ID();
        }
    }

    $toReturn["runIds"] = $runIds;

    wp_reset_postdata();

    if (count($runIds) > 0) {

        if ($type == "unregistered") {
            $args = array(
                "post_type"     => "attendant",
                "meta_query"    => array(
                    'relation'  => 'AND',
                    array(
                        'key'       => 'type',
                        'value'     => 'unregistered',
                        'compare'   => "="
                    ),
                    array(
                        'key'       => 'unregistered_member',
                        'value'     => '"' . $memberId . '"',
                        'compare'   => "LIKE"
                    ),
                ),
            );
        }
        else {
            $args = array(
                "post_type"     => "attendant",
                "meta_query"    => array(
                    'relation'  => 'AND',
                    array(
                        'key'       => 'type',
                        'value'     => 'registered',
                        'compare'   => "="
                    ),
                    array(
                        'key'       => 'registered_member',
                        'value'     => $memberId,
                        'compare'   => "="
                    ),
                ),
            );
        }

        $mmq = array(
            "relation"  => "OR"
        );
        foreach($runIds as $runId) {
            $mmq[] = array(
                "key"       => "run",
                "value"     => '"' . $runId . '"',
                "compare"   => "LIKE"
            );
        }

        $args["meta_query"][] = $mmq;

        $toReturn["args"] = $args;

        $the_query = new WP_Query( $args );

        if ( $the_query->have_posts() ) {
            while ( $the_query->have_posts() ) {
                $the_query->the_post();

                $toReturn["unprocessed"] += 1;
            }
        }

        wp_reset_postdata();

    }

    return $toReturn;

}

The value returned by get_the_ID() in the calling code is a value that comes from the query that is called with the arguments directly beneath "//Get unprocessed runs".

Am I missing something obvious? Am I making a newbie mistake?

How does uc_unprocessedRuns() change what get_the_ID() returns in the calling code?