I'm seeing the following in Safari (MacOS 10.8.5, Safari 6.2.2; also 10.10.1 with 6.2.5), running WeBWorK 2.7 with MathJax 2.4.0 using local STIX fonts). When displaying a fraction such as

\frac{a + \sqrt{b x}}{c + \sqrt{d x}}

the horizontal overbar in the square-root symbol does not display when the zoom is at its default scaling. Increasing---or decreasing---the font-size results in the display appearing as expected.

Does anyone know if this is a quirk or a bug, or something weird with our set-up?

Thanks,

Gavin