As my native language is russian, I have to work with cyrillic filenames.
Here is the result of test with screenshots showing what happens with these names.
1 Let's take file with russian name
2 Upload it to RAZUNA
3 See it in RAZUNA folder
4 Try to play it -- It plays correctly and correct name is displayed
5 Try to download it back -- Here we see filename is INCORRECT
6 Try to download a file with latin name -- everything OK
7 Let's get local path of our russian file on server -- It's name is lost
8 Check server directory -- yes name is broken.