Have you tried replacing all instances of
box.js in our View Cart code with
box_fb_n.js (if you've opted-in to use our new cart) or
box_fb_o.js (if you've opted-out to use our classic cart)?
You would need to do that on every page where you have any View Cart code, and do it for every instance you find on that page (if you have multiple View Carts on the same page).
If you need further help troubleshooting this, we'd need a link to your sales page where you see the problem happening, and your permission to briefly enable the new cart for a few minutes if necessary for testing. Feel free to email that link to us if you'd rather not post it here on the forum.