So I’m currently running a “Buy X get Y” automatic discount on my site: https://woofloof.com/ through the default Shopify discounts, but almost every single customer that’s attempted to make a purchase has had issues applying the discount. I understand the discount should apply automatically once the items have been added to cart.
Unfortunately my customers have, at best, had to refresh their cart/checkout pages multiple times in order for the code to finally be applied, or at worst, still not be able to get the discount applied even after various attempts at refreshing or re-adding their items to cart 
It’s a massive pain for us because most of the time, we end up having to manually apply discounts to draft orders to invoice our customers.
Is there a bug proof / foolproof way to apply a discount like this? Has anyone personally used any apps that were effective and bug-free? Thanks in advance!