For example, I can reproduce your results only when
singleResult=>1is used with the MultiAnswer object. That is important information that we would have had if you had provided a full example.
The issue is due to the fact that when the MultiAnswer object was written, the correct answer in the result table was not displayed in typeset form, but was always an answer string like what a student would enter. The TeX version was added fairly recently, and MultiAnswer hasn't been updated to accommodate that. If you use
singleResult => 0, it will format as you want it to, but the single-result version doesn't generate the required TeX form.
I've attached an updated copy of
parserMultiAnswer.plthat should take care of the problem.