Billing address fields giving error after returning to checkout page from PayPal

Hi,
we are using your plugin for handling Braintree on our webshop, both prodcuction and sandbox.
We are seeing an issue on our Woocommerce-based webshop’s checkout page. The issue is as follows:
-Customer fills out the billing address fields (and possibly shipping address fields, if different) on the Woocommerce page
-Customer selects PayPal as the payment method
-Customer clicks “Place order” button
-PayPal popup appears, and customer handles the PayPal-side of the payment, and clicks on the popup’s button to pursue with payment and ordering, closing the popup
-Then, while we have PayPal configured on the Sandbox side so that PayPal autopopulates billing address details, there is an error taking place on the Woocommerce-checkout page. There is an error note about all the billing address fields, stating “Billing First Name is a required field”, “Billing Last Name is a required field”, etc. This happens even when all of the required billing address fields contain the needed info
-When customer clicks on the “Place Order” button again, the order goes through, even if the customer has then done nothing to the billing address information (=they are unchanged from the moment the customer has typed them in in the fist place)

This issue only appears when there is items in the order that require shipping. Purely subscription-related orders go through without an issue.
We are baffled by this issue, and it is a big inconvenience.
We are not using any other plugin on the checkout page, that should interfere and cause this error.
This also was happening, before PayPal configured our Sandbox account to autopopulate billing address fields.
Your swift help is dearly appreciated!