Thread:Extension talk:SimpleMathJax/Sporadic but very frequent red Math Processing Error instead of formulas

I see a red [Math Processing Error] replacing formulas in my wiki. The formulas themselves are okay. When I refresh the page, some of them are displayed correctly, some of them get replaced by the error message. Once in a while after many refreshes, I see all of the formulas correctly.

What might be the source of this error?