MathJax issue?

This page demonstrates a possible issue with the MathJax explorer. I cannot start the explorer with multi-line displayed mathematics. This appears to be browser independent and independent of whether the mathematics is in LaTeX or MathML. The issue appears to be present whether or not a screenreader is in use.

Process to test:

Right click on an equation and select Accessibility, then Explorer, then Activate.
The first two displayed equations below work as expected. Put the equation in focus using tab and then press shift-space. The explorer is entered and can be used. Esc exits.
The same process does not seem to work for the multi-line mathematics on this page or others.

Working example

The explorer can be used as expected on the following two equations. These are unnumbered single line displayed equations, one in LaTeX and one in MathML.

LaTeX

\begin{equation*}x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\end{equation*}

MathML

x = \frac{- b \pm \sqrt{b^{2} - 4 a c}}{2 a}

Minimal example of issue

The explorer does not work with the following two equations which are unnumbered multi-line equations and which are therefore using mtable.

LaTeX

\begin{align*}x &= \frac{-b \pm \sqrt{b^2-4ac}}{2a}\\ &= \pm 3i\end{align*}

MathML

\begin{array}{l} x & = \frac{- b \pm \sqrt{b^{2} - 4 a c}}{2 a} \\ = \pm 3 i \end{array}

Any help would be gratefully received!