Typesetting gives different results Windows MiKTeX vs Linux TeXLive

Windows:
This is pdfTeX, Version 3.1415926-2.4-1.40.13 (MiKTeX 2.9 64-bit)
(preloaded format=pdflatex 2014.11.19)  4 MAY 2015 20:14

Linux:
This is pdfTeX, Version 3.1415926-2.4-1.40.13 (TeX Live 2012)
 restricted \write18 enabled.

I have lots of packages loaded, so will take a while I guess to narrow
down the problem -- before I begin, I was wondering if this is a
familiar complaint?

Specifically, there is a figure that gets sent to a page of floats on
Windows (at the end of the chapter), but not on Linux, for the same
document. Here is the relevant (simplified) code for that image (it's
the second subfigure -- Figure B):


\begin{figure}[tbh]
    \centering
    \begin{subfigure}{0.8\linewidth}
        \centering
        \includegraphics[width=\linewidth]{figureA}
        \caption{Figure A}
        \label{fig:A}
    \end{subfigure}
    \bigskip

    \begin{subfigure}{0.8\linewidth}
        \centering
        \includegraphics[width=\linewidth]{figureB}
        \caption{Figure B}
        \label{fig:B}
    \end{subfigure}
    \caption{Caption}\label{figureAB}
\end{figure}

If I set the width of the second \includegraphics to be
[width=0.9\linewidth] then the figure doesn't get kicked to its own
page of floats.

Any tips?

Ben.