Index: src/bp-groups/bp-groups-functions.php
===================================================================
--- src/bp-groups/bp-groups-functions.php
+++ src/bp-groups/bp-groups-functions.php
@@ -531,6 +531,12 @@
 		'type'                => 'last_joined',
 	) );
 
+	// querystring 'false' values need to be explicitly cast as a false value
+	// @see https://buddypress.trac.wordpress.org/ticket/6013
+	if ( is_string( $r['exclude_banned'] ) && 'false' === $r['exclude_banned'] ) {
+		$r['exclude_banned'] = 0;
+	}
+
 	// For legacy users. Use of BP_Groups_Member::get_all_for_group()
 	// is deprecated. func_get_args() can't be passed to a function in PHP
 	// 5.2.x, so we create a variable