The Kaching Quantity Bundles app relies on Shopify functions to apply automatic discount codes. However, Shopify Plus custom checkout does not support Shopify functions, leading to limitations in the functionality of our app.

When a shop is on Shopify+ with custom checkout - we fallback our logic to use basic discount codes. In that case, we create a discount code for every deal bar of each deal block.

Using basic discounts with discount codes has a lot of drawbacks. We will always redirect to the cart page after the customer clicks 'Add to cart' in order to apply the discount code automatically.

Only one discount code can be active at a time, so if a customer is buying two products from separate deal blocks only one will apply.

It doesn't support the 'Specific price' discount type and 'All products except selected'.

To clarify, this is a Shopify limitation that we are unable to override. The only workaround for now is to avoid using Shopify's custom checkout.

We are eagerly awaiting updates from the Shopify team to address and resolve this issue.

References:
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​https://shopify.dev/docs/apps/functions