epigraph y titlesec+titletoc crean un mal comportamiento

Question

Utilizo titlesec y titletoc para crear mi propio estilo de capítulo que contiene un minitoc después del título del capítulo. Y uso epígrafe cuando quiero tener uno antes del título del capítulo.

Actualmente estoy escribiendo un capítulo que contiene varias secciones, por lo que el minitoc debe continuar en la página siguiente. Esto lleva a una impresión incorrecta del epígrafe y además las últimas secciones no se imprimen en el siguiente ejemplo:

\documentclass[11pt]{book}
\usepackage[utf8]{inputenc}     
\usepackage[T1]{fontenc}        


\usepackage{titletoc}
\usepackage{titlesec}
    \newlength{\HeightBeforeChap}
    \setlength{\HeightBeforeChap}{0pt}

    % redefine chapter style
    \titleformat{\chapter}[hang]{\filright}{}{0pt} 
        {\vspace*{\HeightBeforeChap} \\! \Huge \bfseries\raggedleft}
        [\vspace*{4pc}%
            \startcontents
            {\raggedright\bfseries \large Mini ToC \endgraf}
            \titlerule
            \vspace{6pt}
            \printcontents{p}{1}{\setcounter{tocdepth}{3}}
            \vspace{6pt}
            \titlerule
        ]

\usepackage{epigraph}
        \renewcommand{\textflush}{flushepinormal}
        \setlength\epigraphwidth{.55\textwidth}
        \makeatletter
            \@ifundefined{HeightBeforeChap}
            {% \HeightBeforeChap not defined
                }
            {% \HeightBeforeChap defined
                \renewcommand{\dropchapter}[1]{\setlength{\HeightBeforeChap}{#1} }
            }%
        \makeatother


\begin{document}

    \dropchapter{11pt}
    \chapter{title 1}

    \epigraphhead[40]{
            \epigraph{\itshape Computer programming is an art, because it applies 
                accumulated knowledge to the world, because it requires skill and ingenuity, 
                and especially because it produces objects of beauty.
            }{Donald Knuth, \textit{"Computer Programming as an Art". Communications of the ACM, Volume 17, Issue 12, dl.acm.org., December 1974}}
        }
    \dropchapter{0cm}

    \section{section 1}
    \subsection{title}
    \subsubsection{title}
    \section{section 2}
    \section{section 3}
    \section{section 4}
        \subsection{title}
        \subsubsection{title}
    \section{section 5}
    \section{section 6}
    \section{section 7}
        \subsection{title}
        \subsubsection{title}
    \section{section 8}
        \subsection{title}
        \subsubsection{title}
    \section{section 9}
        \subsection{title}
        \subsubsection{title}
    \section{section 10}
    \section{section 11}
    \section{section 12}
    \section{section 13}
        \subsection{title}
        \subsubsection{title}
    \section{section 14}
        \subsection{title}
        \subsubsection{title}
    \section{section 15}
        \subsection{title}
        \subsubsection{title}
    \section{section 16}
    \section{section 17}
    \section{section 18}
    \section{section 19}
        \subsection{title}
        \subsubsection{title}
    \section{section 20}
        \subsection{title}
        \subsubsection{title}
    \section{section 21}
        \subsection{title}
        \subsubsection{title}
    \section{section}

    \chapter{title 2}
    \section{title}

\end{document}

Aquí están los resultados que obtengo:

Gracias a la respuesta deegreg, Creo que está relacionado con la terminación de la página necesaria para imprimir el epígrafe, pero no tengo idea de cómo solucionarlo.

Gracias por su ayuda.

Answer 1

Como no hay ni un solo comentario incluso después de la recompensa que ofrecí, se me ocurrió una solución fea, esperando mejores soluciones de SE.

El feo:

\documentclass[11pt]{book}
\usepackage[utf8]{inputenc}     
\usepackage[T1]{fontenc}        

\usepackage{titletoc}
\usepackage{titlesec}
    \newlength{\HeightBeforeChap}
    \setlength{\HeightBeforeChap}{0pt}
    \newcommand{\BeforeChapCmd}{}
    \newcommand{\BeforeChap}[1]{\gdef\BeforeChapCmd{#1}}

    % redefine chapter style
    \titleformat{\chapter}[hang]{\filright}{}{0pt} 
        {\BeforeChapCmd\leavevmode\vspace*{\HeightBeforeChap}\BeforeChap{}\\ \Huge \bfseries\raggedleft}
        [\vspace*{4pc}%
            \startcontents
            {\raggedright\bfseries \large Mini ToC \endgraf}
            \titlerule
            \vspace{6pt}
            \printcontents{p}{1}{\setcounter{tocdepth}{3}}
            \vspace{6pt}
            \titlerule
            \leavevmode
        ]

\usepackage{epigraph}
    \renewcommand{\epigraphhead}[2][]{\BeforeChap{#2}   

\begin{document}

%   \dropchapter{11pt}
    \epigraphhead[40]{
                 \epigraph{\itshape Computer programming is an art, because it applies 
                     accumulated knowledge to the world, because it requires skill and ingenuity, 
                     and especially because it produces objects of beauty.
                 }{Donald Knuth, \textit{"Computer Programming as an Art". Communications of the ACM, Volume 17, Issue 12, dl.acm.org., December 1974}}
             }
    \chapter{title 1}
%    \dropchapter{0cm}

     \section{section 1}
     \subsection{title}
     \subsubsection{title}
     \section{section 2}
     \section{section 3}
     \section{section 4}
         \subsection{title}
         \subsubsection{title}
     \section{section 5}
     \section{section 6}
     \section{section 7}
         \subsection{title}
         \subsubsection{title}
     \section{section 8}
         \subsection{title}
         \subsubsection{title}
     \section{section 9}
         \subsection{title}
         \subsubsection{title}
     \section{section 10}
     \section{section 11}
     \section{section 12}
     \section{section 13}
         \subsection{title}
         \subsubsection{title}
         blabla blabla blabla blabla blabla blabla blabla blabla blabla blabla.
     \section{section 14}
         \subsection{title}
         \subsubsection{title}
     \section{section 15}
         \subsection{title}
         \subsubsection{title}
     \section{section 16}
     \section{section 17}
     \section{section 18}
     \section{section 19}
         \subsection{title}
         \subsubsection{title}
     \section{section 20}
         \subsection{title}
         \subsubsection{title}
     \section{section 21}
         \subsection{title}
         \subsubsection{title}
     \section{section}

     \chapter{title 2}
     \section{title}

\end{document}