$wpdb->delete not working for me

Question

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
        )
      );
    }
  }
}

Answer 1

From the codex page: If omitted, all values in $where will be treated as strings

So try setting $where_format:

  $wpdb->delete(
    $table,
    array(
      'schedule_item_id' => $item->id
    ), 
    array( '%d' )
  );