Problems font display on website and admin in French + lost pictures

Since the last update of WP to 4.7.1, special French letters don’t display correctly. i.e.: “é” has become “??”
This is on website and on admin
I also have pictures problems from the library: all images that have special letters in the description cannot be used or displayed.
I tried to desactivate all pulgins to check if one of them created the problem but it didn’t solve anything.
One solution is to type the text again (it works) but is too long and this shouldn’t have happened