So, I’ve figured it out. The problem was in the settings of a caching plugin, which I did myself of course. I am no longer getting ‘mathzoom failed to load’ messages after resetting the caching plugin. To state exactly, I was using the LS Cache plugin with “JS Combine External and Inline” enabled. Once I disabled it, the “mathzoom js failed to load” problem disappeared.
I am also having exactly the same issue on my QSM quizzes. I am talking about General Knowledge and English tests, which don’t even contain any Math text. Please help.