You can add any product from my store and then go to checkout. https://amandaduncan.com/store/
You’ll see the order bump with 60% off but when it gets added to the cart it doesn’t show the discount.
This is what I have on the backend. https://drive.google.com/file/d/1Y64HCHA1jhy-R_KoHN-ZG7LYA1-qBwY6/view?usp=sharing
I’m experiencing this only in Firefox.