As the title implies, this problem did not occur before the sketch was exported.
The specific error is:
java.lang.RuntimeException: Could not load font typewrite.vlw. Make sure that the font has been copied to the data folder of your sketch.
The setup code is:
MAP = systemFileMapper()
f = loadFont(“typewrite.vlw”)
After testing, it seems as if it has nothing to do with the specific font file, and looking into the created application, the data file does contain the “typewrite.vlw”.
Other exported python sketches have been able to run with no problem before (although they didn’t have any fonts in them), so it is something to do directly with Processing’s font system once exported.