Adding full price discount causing error with PayPal

Hello,
When proceeding to the cart page, if the user enters a discount code that covers the full price of the items in the cart and clicks the Apply Discount button, the discount applies correctly and the total price updates to show zero. However, the PayPal buttons remain displayed and if the user clicks on one of them an error message is displayed saying:
Payment failed. Please review your information and try again.

If the Update Cart button is clicked, the entire page refreshes and the PayPal buttons are not displayed. Instead the Checkout button appears and clicking it allows the user to proceed and complete the checkout process.

It seems like the ajax process that is triggered when clicking the Apply Discount button should check to see if the PayPal buttons should be displayed or not and if the Checkout button should be displayed or not, based on the new order total.

Also, if I go to the cart page and a discount code has already been applied that has zeroed out the order total, the PayPal buttons do not appear and the Checkout button is displayed (which is correct), but if I click to remove the discount, the order total is refreshed correctly, but the PayPal buttons don't appear and the Checkout button remains.