Linked sequence only runs once in the browser
I've been trying to debug a student's experiment, and have run into a wall: the script runs fine locally, but only runs the sequence "Letters_choice_sequence" the first time around (during the practice run), despite the fact that the sequences are all linked, and should be exactly the same. I have run out of ideas; maybe somebody else can spot what I cannot?
The script is attached; it is just a skeleton, so you have to hit a key to advance in places where you might expect it to advance automatically, etc. It is just the running of "Letters_choice_sequence" in the browser that I can't figure out.
Thanks in advance to anyone willing to take a look at this!