Hi Mike,
When you say you have the option set to auto-approve sales, can you please clarify what you are referring to? By default, there is not a way to auto-complete orders automatically, but I see that you are using the WooCommerce Autocomplete Orders plugin. Can you tell me what you have set under WooCommerce > Settings > Extra Options > Autocomplete Orders?
Also, is it just ticket orders that this is happening on, or is it occurring with other orders on your site as well that do not contain tickets?