`frame` doesn't retain centers

[wspr]

trafficstars

Hard to describe in words; the following examples share a right edge rather than a centre line:

\begin{dmath}[frame]
F(s) = \laplace
\end{dmath}

\setlength\fboxrule{1mm}
\begin{dmath}[frame]
F(s) = \laplace
\end{dmath}

\begin{dmath}[frame=2pt]
F(s) = \laplace
\end{dmath}

[wspr]

This is more easily seen with enlarged framesep values.