Sorry, you're right, it doesn't seem to work every time. It is dated 2013 so perhaps it is no longer maintained.
However, it is the work of Nick Heard who seems to have updated it. The part below seems to work now...
http://www.heardfamilyhistory.org.uk/index.htmlinc e-mail contact link
Actually dated 2015 so you may find something or contact Nick.
Good luck.