I haven't seen this before but it's possible there is a bug here.
What would be most helpful would be to post this to bugzilla
(the module is the Problem.pm although it's not vitale that you specify)
If you can submit to bugzilla while editing the page containing the
problem and while acting as the student -- that will send the most
Submitting screen shots of the student's page after answering the problem,
particularly the material at the bottom which lists the current score, the
cumulative score (i.e. the highest score so far). Then also a screen shot
of the past answer list for this student. There may be clues in those two
Thanks for the report.
Has anyone else experienced this phenomenon?