I am having issues with the Checkout Button in the Cart working sometimes but not all others.
I experienced the same issue in IE and Chrome & Incognito mode. When you first add the items to the cart and go to checkout it works. If you hit the back button and remove and add anything else to the cart it no longer works. Not sure what the issue is or where to start looking.
I looked over the previous issues and disabled the product recommendations that pops up on that page and it didn't change the issue.
Just not sure where to start looking. I even went to old theme files and still have the same issue.