alignment issue with glbreaking (gloss breaking) in expex

Question

I have set up a layout using paracol with expex glosses in one column and regular text in the other column directly across.

At the page break of the MWE below, you can see that the regular-text column does not stay in alignment with the gloss. I have even added and adjusted a special strut just for that final paragraph but to no avail (if you adjust the strut so that the regular text moves over to the next page, then it does not come close to aligning properly). Most of the time, the gloss page breaks work just fine, but special cases like this do happen regularly over a long document.

How can the code be adjusted to yield proper alignment, even when this happens at a page break in the middle of a document?

Note: you must use the latest expex package for the glbreaking feature to work.

MWE (XeTeX):

\documentclass{book}

\usepackage{microtype}

\usepackage[
    paperwidth=7.5in,
    paperheight=9.25in,
    inner=0.5in,
    outer=0.5in,
    bindingoffset=0.25in,
    top=0.75in,
    bottom=1.25in,
    twoside,
    %showframe
    ]
    {geometry} 

\usepackage{paracol}
    \twosided[pc]

\usepackage{polyglossia}
    \setdefaultlanguage{english}
    \setotherlanguage{hebrew}
    \newfontfamily\hebrewfont[Script=Hebrew]{Arial}
    \newfontfamily\englishfont{Linux Libertine O}

\usepackage{expex}

\lingset{
    everygla=\Large, 
    everyglb=\scriptsize\englishfont\it,
    everyglc=\scriptsize\englishfont,
    glwordalign=center,
    glhangindent=0em,
    glrightskip=0pt,
    glhangstyle=none,
    aboveglbskip=-0.7ex,
    aboveglcskip=-0.7ex,
    glbreaking
}

\columnratio{0.71}
\setlength{\columnsep}{1.0em}

\newenvironment{interlinearfirst}%
    {\begin{leftcolumn*}\begin{hebrew}\mystrutfirsta\sloppy\begingl}%
    {\endgl\end{hebrew}\end{leftcolumn*}}
\newenvironment{translationfirst}%
    {\begin{rightcolumn}
    \footnotesize\noindent\ignorespaces\mystrutfirstb\sloppy}
    {\end{rightcolumn}}

\newcommand{\mystrutfirsta}{\rule{0pt}{0pt}}
\newcommand{\mystrutfirstb}{\rule{0pt}{22pt}}

\newenvironment{interlinear}%
    {\begin{leftcolumn*}\begin{hebrew}\mystruta\sloppy\begingl}%
    {\endgl\end{hebrew}\end{leftcolumn*}}
\newenvironment{translation}%
    {\begin{rightcolumn}
    \footnotesize\noindent\ignorespaces\mystrutb\sloppy}
    {\end{rightcolumn}}

\newcommand{\mystruta}{\rule{0pt}{0pt}}
\newcommand{\mystrutb}{\rule{0pt}{12pt}}

\newenvironment{interlinearspecial}%
    {\begin{leftcolumn*}\begin{hebrew}\mystrutc\sloppy\begingl}%
    {\endgl\end{hebrew}\end{leftcolumn*}}
\newenvironment{translationspecial}%
    {\begin{rightcolumn}
    \footnotesize\noindent\ignorespaces\mystrutd\sloppy}
    {\end{rightcolumn}}

\newcommand{\mystrutc}{\rule{0pt}{0pt}}
\newcommand{\mystrutd}{\rule{0pt}{13pt}}%adjust this strut for the last paragraph

\begin{document}
\begin{paracol}{2}

\begin{interlinearfirst}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinearfirst}

\begin{translationfirst}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translationfirst}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinearspecial}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinearspecial}

\begin{translationspecial}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translationspecial}

\end{paracol}
\end{document}

Output:

Answer 1

The following is semi-automated solution. The paracol package provides a \flushpage command to clear the end parallel pair and and start a new page.

This, in conjunction with the \strut you've added in the {translationspecial} will line up the parallel columns correctly again. (I think the alignment problem is due to paracol not ExPex).

Although not totally automatic, I've made things a bit simpler so that you don't need the special versions of your environments. Instead I've created a \flushtrans command which issues the \flushpage command and then sets a conditional to trigger use the right size \strut command.

So whenever you have a bad break, issue a \flushtrans command before the relevant {interlinear} environment, and the rest will happen automatically.

We can use the same technique to eliminate the need for your translationfirst and interlinearfirst environments. Instead I've added a second conditional which is set at the beginning of a paracol environment. This will be used inside the translation environment to use the correct strut.

\documentclass{book}

\usepackage{microtype}

\usepackage[
    paperwidth=7.5in,
    paperheight=9.25in,
    inner=0.5in,
    outer=0.5in,
    bindingoffset=0.25in,
    top=0.75in,
    bottom=1.25in,
    twoside,
    showframe
    ]
    {geometry} 

\usepackage{paracol}
    \twosided[pc]

\usepackage{polyglossia}
    \setdefaultlanguage{english}
    \setotherlanguage{hebrew}
    \newfontfamily\hebrewfont[Script=Hebrew]{David CLM}
    \newfontfamily\englishfont{Linux Libertine O}

\usepackage{expex}

\lingset{
    everygla=\Large, 
    everyglb=\scriptsize\englishfont\it,
    everyglc=\scriptsize\englishfont,
    glwordalign=center,
    glhangindent=0em,
    glrightskip=0pt,
    glhangstyle=none,
    aboveglbskip=-0.7ex,
    aboveglcskip=-0.7ex,
    glbreaking
}


\columnratio{0.71}
\setlength{\columnsep}{1.0em}
\newif\iftranslationspecial
\newif\iffirst
\newcommand\flushtrans{\flushpage\translationspecialtrue}
\AtBeginEnvironment{paracol}{\firsttrue}

\newcommand{\mystrutfirsta}{\rule{0pt}{0pt}}
\newcommand{\mystrutfirstb}{\rule{0pt}{22pt}}

\newenvironment{interlinear}%
    {\begin{leftcolumn*}\begin{hebrew}\mystruta\sloppy\begingl}%
    {\endgl\end{hebrew}\end{leftcolumn*}}

\newenvironment{translation}%
    {\begin{rightcolumn}
\footnotesize\noindent\ignorespaces\iffirst\mystrutfirstb\else\iftranslationspecial\mystrutd\else\mystrutb\fi\fi\sloppy}
    {\end{rightcolumn}\global\translationspecialfalse\global\firstfalse}

\newcommand{\mystruta}{\rule{0pt}{0pt}}
\newcommand{\mystrutb}{\rule{0pt}{12pt}}
\newcommand{\mystrutc}{\rule{0pt}{0pt}}
\newcommand{\mystrutd}{\rule{0pt}{20pt}}%adjust this strut for the last paragraph

\begin{document}
\begin{paracol}{2}
\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}
\flushtrans % added this

\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}
\begin{interlinear}
  \gla אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד אאאאא בבבבב גגגגג דדדדד  //

  \glb aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //

  \glc aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd aaaaa bbbbb ggggg ddddd //
\end{interlinear}

\begin{translation}%
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there live the blind texts. Separated they live in Bookmarksgrove right at the coast of the Semantics, a large language ocean. A small river named Duden flows by their place and supplies it with the necessary regelialia.
\end{translation}

\end{paracol}
\end{document}