The Ruby script that process the map configuration information given in the map form is very particular about what information it will accept. For example, if you enter a Maidenhead grid as fn31 instead of FN31, the program will not produce a map because the first two letters are supposed to be upper case. Similarly, the title will be rejected if it has non-printable or non-ASCII characters.
I wrote the program to be very strict about checking its inputs to ensure that people cannot cause the program to generate a hostile PDF. Rather than trying to identify and detect all the bad things a malicious person might enter to generate malicious output, I have instead tried to ensure that only safe characters are allowed in the input.