My GoogleFu has failed me, and I can't find anyone else this has applied to. We're running ~ 600 quizzes per week in WeBWorK, and in the last two weeks I've had two students who've had questions not render properly. Refreshing / logging back in doesn't seem to work. It's a gateway/quiz setup, 15 minute limit. They've both seem something like the attached image, where all the options of the multiple choice are replaced by "[math]".
In the second case, I know the student's details: he was running the latest version of Google Chrome on Mac OSX 10.12. I don't recall the first time it happened.
Unfortunately, with the randomization of questions, it's hard to be able to tell what the solutions for a given student should be, so I've just overwritten the score for these two students. I'd like to figure out what's going on, though, so I can fix it in general, or at least have a workaround for the TAs to use.