I have done the following:
I used the "net use lpt1: \\server\share" method as suggested by Lonkero and this has no effect on the problem. Obviously the program does not use the parallel port scenario.
I attemped to use the process monitor, but I couldn't work out what to filter, and I ran out of time to look at it. I will look into the matter when I have more time, but what I will do longterm is use the converted vbs coding as suggested by Arend as this works flawlessly. But I will attempt to find the cause of the issue and post the solution. Many thanks for all the advice so far.