Getting ‘Function ID was called incorrectly’

Firstly a huge thank you for such a useful plugin I use it all the time to confirm tweaks to woo emails. I am getting the following error when choosing an order ID from the admin menu: Function ID was called incorrectly

It looks like you access ID directly in form.php, eg

<option value="<?php echo $order->ID ?>" <?php selected( $order->ID, $this->orderID ); ?> >#order : <?php echo $order->ID; ?></option>

I believe ID should be accessed indirectly like this:

$order->get_id();

Changing this fixes the errors.