Changes are not saved.

I think it’s a conflict. I would recommend running a full conflict test as described here: https://docs.woocommerce.com/document/woocommerce-self-service-guide/

It’s very possible that another plugin (or possibly even your theme) is causing the trouble, and this will help you identify the culprit.

Please open a ticket on our Support Forum if you need help: https://wordpress.org/support/plugin/bopo-woo-product-bundle-builder/