I have attached the screenshots here, On checkout page customer is login, when I select first address and click on update, shows like this, anyone has idea about it? This is default braintree payment gateway configured.
I faced with this problem on v2.4.1 :)
The solution is to remove _.values for currentBillingAddress().street in in the file "vendor/magento/module-checkout/view/frontend/web/template/billing-address/details.html"
Should be: "currentBillingAddress().street.join(', ')"
Need to overwrite this html file in theme to apply.
This solved the problem for me. https://github.com/magento/magento2/issues/25684