reverted:
--- b/core/lib/Drupal/Component/Archiver/ArchiveTar.php
+++ a/core/lib/Drupal/Component/Archiver/ArchiveTar.php
@@ -975,7 +975,7 @@
       }
 
       // ----- Calculate the stored filename
+      $p_filename = $this->_translateWinPath($p_filename, false);;
-      $p_filename = $this->_translateWinPath($p_filename, false);
       $v_stored_filename = $p_filename;
       if (strcmp($p_filename, $p_remove_dir) == 0) {
           return true;
@@ -1038,7 +1038,7 @@
       }
 
       // ----- Calculate the stored filename
+      $p_filename = $this->_translateWinPath($p_filename, false);;
-      $p_filename = $this->_translateWinPath($p_filename, false);
 
       if (!$this->_writeHeaderBlock($p_filename, strlen($p_string),
 	                                  time(), 384, "", 0, 0))