$wpdb->delete not working for me

I have a function (see in full below) that syncs data into WP from an external database. It's a list of scheduled items. When the schedule is updated, old data should be deleted. See this snippet:

$wpdb-delete(
        $table,
        array(
          'schedule_item_id' = $item-id
        )
)

But this is not happening. For example if I have an item A scheduled on a Tuesday at 6pm, then I remove that from the external database and I replace it with ietm B scheduled at the same time. WordPress should delete item A, but it doesn't. I see both items A and B on the schedule. $wpdb-delete is not removing it. Am I doing something wrong here? Here's the complete function:

function sync_schedule($scheduleItems) {
  global $wpdb;
  foreach($scheduleItems as $item) {
    if (!$item-show) { continue; }
    $table = $wpdb-prefix . 'schedule_items';
    $existing_row = $wpdb-get_row($wpdb-prepare(SELECT * FROM $table WHERE schedule_item_id=%d, $item-id));
    $show = get_show_post_by_id($item-show);
    if (!$show) { continue; }
    if (empty($existing_row)  $item-deleted == FALSE) {
      $wpdb-insert(
        $table,
            array(
                'run_date_time' = $item-runDateTime,
                'show_id' = $item-show,
            'show_title' = $show-post_title,
            'show_post_id' = $show-ID,
            'channel_id' = $item-channel,
            'channel_post_id' = 0,
            'schedule_item_id' = $item-id
            )
      );
    } else if ($item-deleted == FALSE){
      $wpdb-update(
        $table,
        array(
          'run_date_time' = $item-runDateTime,
          'show_id' = $item-show,
          'show_title' = $show-post_title,
          'show_post_id' = $show-ID,
          'channel_id' = $item-channel,
          'channel_post_id' = 99,
          'schedule_item_id' = $item-id
        ),
        array(
          'schedule_item_id' = $item-id
        )
      );
    } else {
      $wpdb-delete(
        $table,
        array(
          'schedule_item_id' = $item-id
        )
      );
    }
  }
}