Hi again,
I figured it out... sort of.
The min-max in my style file had a "!" after the "0-2500", which was apparently creating a conflict by telling the program that it had to terminate and proceed after the set time even though it was also requiring a response. So after removing the "!" it doesn't crash when I don't provide a response. However, it just sits there and waits until a response is given, rather than moving on to the next trial after 2500ms.

Is there some way to work around that and get it to both require the correct response (if participants respond), AND move on after 2500ms if they don't?

(I'll work on getting it zipped and uploaded so you can take a look)