Hi finally i found a way! Thank for your help. The only way to make it work is t open a new empty file, to create the blank glyphs, to copy and to paste it in the current file, and no error… Can’t explain why but it is fixed.
Or select all glyphs and run Update Glyph Info. You may want to revise Font Info > Other > Custom Glyph Names and make sure that there is no custom glyph info (indicated with an info symbol in Font View).
Can you update to the latest cutting edge version. It will warn you about the double encoding when you add the new glyph. And I just tried, ‘Glyph > Update Glyph Info’ will clear the double encoding.