Windows doesn't accept the '/' character, so you can't create a file using the '/' character, which is why the validation fails. You would have to alter the file name to remove the '/' from the name to an acceptable alternative or consider using an alternative character in their order numbers to avoid this issue in the future.
The following characters should be avoided in FactoryMaster:
\ Backslash
, Comma
‘’ Single quote marks
“ Double quotes
* Asterisk
? Question mark
& Ampersand
% Percentage
_ Under score
- Hyphen