Index: wp-includes/class-wp-customize-manager.php
===================================================================
--- wp-includes/class-wp-customize-manager.php	(revision 22339)
+++ wp-includes/class-wp-customize-manager.php	(working copy)
@@ -652,8 +652,10 @@
 		$ap = $a->priority;
 		$bp = $b->priority;
 
-		if ( $ap == $bp )
-			return 0;
+		if ( $ap == $bp ) {
+			$section_keys = array_keys( $this->sections );
+			return array_search( $a->id, $section_keys ) < array_search( $b->id, $section_keys );
+		}
 		return ( $ap > $bp ) ? 1 : -1;
 	}