MC-36598: Default Billing address is not selected after the same address checkbox unticked

Author: victor-v-rad

app/code/Magento/Checkout/view/frontend/web/js/view/billing-address/list.js

@@ -23,6 +23,9 @@ define([
         },
         addressOptions = addressList().filter(function (address) {
             return address.getType() === 'customer-address';
+        }),
+        addressDefaultIndex = addressOptions.findIndex(function (address) {
+            return address.isDefaultBilling();
         });
 
     return Component.extend({
@@ -53,7 +56,8 @@ define([
             this._super()
                 .observe('selectedAddress isNewAddressSelected')
                 .observe({
-                    isNewAddressSelected: !customer.isLoggedIn() || !addressOptions.length
+                    isNewAddressSelected: !customer.isLoggedIn() || !addressOptions.length,
+                    selectedAddress: this.addressOptions[addressDefaultIndex]
                 });
 
             return this;