We fixed this issue in Mosaic version 22.2.1.0.
If the filename meets the requirements and doesn’t include a character not listed in the message, check the value of the filenameAllowedCharsRegex system property. The default recommended value is:
^[\.0-9a-zA-Z_\-=&\+ ',\(\)]*$
You can add or remove characters as needed locally but confirm any changes with your IT security team. Enter the values in the Mosaic config tools exactly as shown above. Don’t surround them with quotation marks, since the value must be written as a REGEX expression.