Please only use basic characters (a-z, A-Z, 0-9, and "-" or "_") in filenames.
Or, in another way, don't use fancy characters in filenames such as accented characters, punctuation such as: "?", ".", ",", "'", because they can cause various problems with file upload and so forth.
Below is a concrete example. The file was saved with the name "comment vous appelez-vous?.mp3". When it was downloaded the question mark was replaced with an underscore, so the new filename is now "comment vous appelez-vous_.mp3". You will see below that the system thinks that the published file and the downloaded file is different (indicated by the yellow):
So, please keep filenames simple: only alphabetic characters, numbers or simple dashes ("-" or "_").