Dear Norbert:I see. I'm not that good to vouch for or against the correctness of the bugfix (if you are speaking about http://tex.stackexchange.com/questions/351377/french-add-usepackagefontspec-to-the-preamble-of-your-document) *alone*, but I trust you knowing latex better than me.
Thank you a lot in any case, I really appreciate that! Leon