Well, it's been a week and I've tried tinkering with some stuff (e.g. removing nonwords.txt and replacing it with a different nonwords.txt) but that didn't make any difference.
Has any progress been made on figuring out what the problem is on your end? If there is no solution, is there some way I can get around this?
Sorry for the delay. It looks like the error messages were tied to weird formatting of your nonwords stimlist. Although it looks like all of the stimlui are properly defined when that stimlist is opened in a program like Notepad, there were spaces without ~ between the last three words in the list when I opened it in Microsoft Word. I fixed the formatting in the attached stimlist and ran it without any errors in the TrackPerformance file. Give it a try and let me know if it works for you.