Hi. I had a frustrated client who was having problems uploading a PDF that had a hash symbol # in the filename. It didn't work, of course, and they came to me for help with it.
Since CMS editors may or may not be aware of what is and what isn't allowed in a filename, I suggest that you display a warning when a filename is incorrect rather than attempting to upload and link to the file.
This might be more user-friendly. :-)
Thanks for listening.
Ken