Why is it showing $0 price and no product image on the cart page?

It's a known issue and it's because Shopify is indexing your products at the back during variants creation. Usually, it takes 10 - 20 seconds for Shopify to finish the loading. Rest assured that the variants are created at the correct price. Customers cannot check out the item for free. 

Shopify is stuck at loading the new variants. Currently, there is no way to speed up the process. There are 3 workarounds here:

1. You can show a notice on the bundle page asking users to refresh the cart page, e.g. Please wait for a few seconds on the cart page so the products can be loaded. You can add a custom style in BYOB Dashboard => Change Design => BYOB Bundle Info Section => Custom CSS. Just copy and paste this 1-liner and hit save:
   .byob-bundle-description-warning { display: block; }
2. Bypass the cart page. Activate 'direct checkout' option in Change Design => BYOB Confirm Pop-up. Customers will be redirected to the checkout page
3. Use discount code bundles. There are no variants created. The bundle price is adjusted with native Shopify discounts. 

If you want to follow the latest fix, you can subscribe to this thread on the Shopify community.