Sounds a lot like my life a couple of years ago (and intermittently since). I don't get the bug reports any more because I think customer service has learned that file name problems can be fixed by renaming the files. Not fun for the user, but a sure fix.
Ya know what kind of file names work virtually everywhere? ASCII ones.
This is a mis-use of ASCII. After all, the colon, asterisk, forward slash, question mark, backward slash, and NUL characters are all in ASCII, yet they are far from things that "work virtually everywhere". And that isn't even considering the open and close square bracket and semi-colon characters which are also not anywhere near portable to the extent of "working virtually everywhere".
The kind of file names that do work "virtually everywhere" are not ASCII, but rather are those who only use characters from the POSIX Portable Filename Character Set, which at 65 characters is just over half the size of ASCII (which has 128 characters).
Ya know what kind of file names work virtually everywhere? ASCII ones.