Found a possible fix that seems to work
In the tickets template the form submit URL goes off to the basket/cart
<form action=”<?php echo esc_url( $woocommerce->cart->get_cart_url() ) ?>” class=”cart” method=”post” enctype=’multipart/form-data’>
Changed to checkout
<form action=”<?php echo esc_url( $woocommerce->cart->get_checkout_url() ) ?>” class=”cart” method=”post” enctype=’multipart/form-data’>
Using this page
https://www.skyverge.com/blog/get-woocommerce-page-urls/