Scanning folders/files with special characters fails

Scanning of my folder works fine most of the time, but not for all comics. I find that Ubooquity overlooks many files: I'm missing entire folders and the comics inside, and I'm also missing files inside folders. I believe this comes from special charaters used in folder names (and I suspect accents like é,é,ü). For example I have a folder named "Valérian" containg 20+ cbz files: none of them are visible in ubooquity. In "corto Maltesse" folder I'm missing "Mü", or "Les Éthiopiques" !

Am I missing something, some settings I didn't find, or is it an undetected bug (which would be strange considering how common are special characters in French comics title)?