Also couldn’t reproduce this with default note type (although I’m not on mac). So I suppose it’s either the type-answer issue, or you are using it in combination with something else (the double closing braces can cause an issue when used inside a cloze deletion – solved by separating them with a space).
If you need to make mathjax work with typing cards, you might want to have a look at this template, that displays both raw-code typing corrections and the rendered result.