Hi,
Thank you for reaching out.
I see no problem with the buttons when one is marked ‘pre-order’: https://snipboard.io/NdfxKA.jpg
It could be possible that a theme or plugin conflict is causing this behavior. In this case, we would recommend testing by taking the following steps: https://docs.woocommerce.com/document/woocommerce-self-service-guide/
If you don’t want to perform these tests on the live site, I would recommend reaching out to your web host to see if they offer a staging site as part of your hosting package. If not, then I’d recommend using the WP Staging plugin to duplicate the site.
Let me know how it goes!
Kind regards.
