How to change the \endhead in the middle of longtable without using two tables?

Question

I am trying to build a long table (and not two tables stuck together). The first two pages should have the same heading while the last one should change to another heading. I tried using the code in this question (Change \endhead in the middle of a longtable), however, my caption comes at the very beginning just after \begin(longtable) and this causes the following error to \endfirsthead and \endhead "Package longtable error: Longtable head or foot not at the start of the table".

Using the same example in the mentioned question, just after adding a caption after \begin(longtable) an error appears. I just need to add a caption as the first thing of the table heading and be repeated with the heading once a new page occurs. Here is the code with that causes the error:

\documentclass[a4paper]{scrartcl}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[utf8]{inputenc}
\usepackage{booktabs}
\usepackage{longtable}
\begin{document}
\newbox\LTheadsave
\makeatletter
\newcommand\saveLThead{\noalign{\global\setbox\LTheadsave\copy\LT@head}}
\newcommand\restoreLThead{\noalign{\global\setbox\LT@head\copy\LTheadsave}}
\makeatother
\setcounter{LTchunksize}{2}
\begin{longtable}{lc}
\caption{Example error}
\toprule
Question 1 & N \
\cmidrule(r){1-1}
\cmidrule(l){2-2}
\endfirsthead
\multicolumn{2}{@{}l}{\textbf{Table} \ref{tab: example} continued}\
\toprule
%\textbf{Table} \ref{tab: example} xyz\
Question 2 (cont.) 1 & N \
\cmidrule(r){1-1}
\cmidrule(l){2-2}
\endhead\saveLThead
\multicolumn{2}{@{}l}{\textbf{Table} \ref{tab: example} continued}\
\toprule
%\textbf{Table} \ref{tab: example} xyz\
Question 1 (cont.) 1 & N \
\cmidrule(r){1-1}
\cmidrule(l){2-2}
\endhead
\bottomrule\endfoot
Item 1 & 4 \
Item 2 & 10 \
Item 3 & 2 \
Item 4 & 8 \
Item 5 & 20 \
Item 6 & 3 \
Item 7 & 6 \
Item 8 & 1 \
Item 9 & 11 \
Item 10 & 6 \
& \\newpage
Item 1 & 4 \
Item 2 & 10 \
Item 3 & 2 \
Item 4 & 8 \
Item 5 & 20 \
Item 6 & 3 \
Item 7 & 6 \
Item 8 & 1 \
Item 9 & 11 \
Item 10 & 6 \
&\
Question 2   & N \
\cmidrule(r){1-1}
\cmidrule(l){2-2}
Item 1 & 4 \\restoreLThead
Item 2 & 10 \
Item 3 & 2 \
Item 4 & 8 \
Item 5 & 20 \
Item 6 & 3 \\newpage
Item 7 & 6 \
Item 8 & 1 \
Item 9 & 11 \
Item 10 & 6 \
\label{tab: example}
\end{longtable}
\end{document}

Any help in this please!

Thank you. Zeinab (She/her)

Answer 1

You can only change the header between chunks, so \LTchunksize is important. In this example there is only one row per page, hence \def\LTchunksize{1}.

I went to some effort to not change the size of \LT@head, although I don't know if that was really necessary.

\documentclass{article}
\usepackage{longtable}
\usepackage{blindtext}
\makeatletter
\newcommand{\changehead}[1]% #1 = tabular...
{\bgroup
  \sbox0{\makebox[\wd\LT@head][c]{\raisebox{0pt}[\ht\LT@head][\dp\LT@head]{#1}}}%
  \global\setbox\LT@head=\copy0
\egroup}
\makeatother
\begin{document}
\begin{longtable}{p{2in}}
  \multicolumn{1}{c}{Inital Definition}\
\endhead
\def\LTchunksize{1}% must go after headers
\blindtext\
\changehead{\begin{tabular}[b]{c}New Definition\end{tabular}}
\blindtext
\end{longtable}
\end{document}