I found a quirk (bug) in the last version and a commented out piece of code. The problem stems from the original being written in about 2000 and while it has been updated it had old architecture that could not be easily modernised so I wrote a new front end for it and copied the guts of the original into it. Had a subclass commented out that I forgot to uncomment and also found an ancient bug that has been there since the original was written.
All fixed and working properly. New version attached.