Basis of overlay used when processing Twenty Twenty-Two checkout.

plugins/woocommerce/legacy/css/twenty-twenty-two.scss

@@ -855,6 +855,8 @@ $tt2-gray: #f7f7f7;
 	}
 
 	.woocommerce-checkout {
+		display: table;
+
 		h3 {
 			font-family: inherit;
 			font-size: var(--wp--preset--font-size--normal);
@@ -866,6 +868,11 @@ $tt2-gray: #f7f7f7;
 			float: right;
 		}
 
+		.blockUI.blockOverlay {
+			position: relative;
+			@include loader();
+		}
+
 		#customer_details {
 			width: 53%;
 			float: left;