Paypal Express Failing After 4.3.9 Update

PayPal Express orders using credit cards are failing after updating to CS-Cart 4.3.9

The settings haven't changed, and our PayPal Pro credit card orders are working fine.

When the customer selects PayPal Express in the cart, gets directed to PayPal, and tries to submit payment, they get a blank screen or the CS-Cart error message: "The transaction cannot be processed. Please enter a valid credit card number and type".

The PayPal API response says the orders fail due to incorrect credit card number, expiration month, and expiration year.

Seems like CS-Cart isn't receiving the credit card info back from PayPal properly, and I'm not sure where to look for the problem.