Using multi-site in sub-domain mode with domain mapping the Editor does not work due to x-frame options error

Console error
Refused to display 'https://mapped-domain.com/?elementor-preview=1208&ver=1525119563' in a frame because it set 'X-Frame-Options' to 'sameorigin'.

This was originally fixed with patch #2151

Has re-appeared somewhere after 2.0 - Can't give specific minor version as we upgraded to 2.0 and skipped further production upgrades until 2.0.8