2 tables in document - error message 'Something's wrong--perhaps a missing \item. \end{tabularx}'

Question

I have two tables in my document but when I compile I get the error message

Something's wrong--perhaps a missing \item. \end{tabularx}

When compiling the document with only one table there is no problem. When compiling document with both tables there is an error message but I can see both tables.

It looks like enumerate can cause problems. I have tried to follow suggestions from TEX link but with no success.

Can someone suggest a way to resolve the error please?

MWE:

\documentclass[a4paper,12pt]{article}
\usepackage{color}
\usepackage{graphicx, epstopdf}
\usepackage[british]{babel}
%\usepackage{gensymb}
\usepackage[section]{placeins}%Allows you to permanently fix figures. 
\usepackage{titleps}%fancy page borders? 
\usepackage[left=2.5cm, right=2.5cm, top=3.5cm, bottom=3.5cm]{geometry}%this changes the page geometry i.e. margins left, right, top and bottom
%\usepackage{caption}
\usepackage{microtype}
\usepackage{setspace}
\usepackage{amsmath}
\usepackage{SIunits}
\usepackage{mathptmx}
\usepackage{tabularx}
\usepackage{booktabs,caption, makecell}
\usepackage{pdflscape,afterpage}
\onehalfspacing

\usepackage{geometry}
\usepackage{booktabs, makecell, ltablex}
\usepackage{caption}

\renewcommand\theadfont{\small\bfseries}
\renewcommand\tabularxcolumn[1]{m{#1}}
\usepackage[usestackEOL]{stackengine}

\usepackage[table]{xcolor}

\usepackage{pdflscape,afterpage}

\usepackage{enumitem}   % <--- added
\usepackage{etoolbox}   % <--- added
\AtBeginEnvironment{table}{%
    \setlist[enumerate]{nosep,     % <--- added
        topsep     = 0pt,
        partopsep  = 0pt,
        leftmargin = *         ,
        before     = \vspace{-0.6\baselineskip},
        after      = \vspace{-\baselineskip}
}}

\begin{document}
    \begin{table}[ht]
        \caption{Cognitive walkthrough goals, tasks and actions}
        \label{table:comparison of techniques}
        \small
        \begin{tabularx}{\linewidth}{@{}
                X
                >{\centering\arraybackslash}X  % content of `X` column is now centered
                X
                @{}}
            \toprule
            \thead{\textbf{Goal}}& \thead{\textbf{Task}} & \thead{\textbf{Action}} \\
            \midrule
            Evaluate the ease in which users can join projects
            &   Access and account set up
            &   \begin{enumerate}
                \item   Teast A: Video provides a powerful way to help you prove your point.

                Test B: Video provides a powerful way to help you prove your point.
                \item Video provides a powerful way to help you prove your point.
            \end{enumerate}     \\
            \addlinespace
            Evaluate the ease in learning to map
            &   Learning how to map
            &   Read tutorial   \\
            \addlinespace
            Contribute data
            &   Contributing data by classifying maps
            &   \begin{enumerate}
                \item Video provides a powerful way to help you prove your point.
                \item Test A: Video provides a powerful way to help you prove your point.

                Test B: Video provides a powerful way to help you prove your point.
                \item Video provides a powerful way to help you prove your point.
            \end{enumerate}     \\
            \addlinespace
            Evaluate if the user likes using the application and whether they like using it
            & -- & --                   \\
            \bottomrule
        \end{tabularx}%
    \end{table}

\begin{landscape}% Landscape page
    \small
    \setlength\extrarowheight{2pt}
    \begin{tabularx}{\linewidth}{
            >{\columncolor{red!30}} l
            *{3}{X}X@{}
        }\caption{}
        %\label{table:comparison of techniques}
        \\
        \Xhline{1pt}
        \multicolumn{1}{c}{\cellcolor{red!30}}
        &\bfseries{Is the effect of the current action the same as the user's goals?}{\cellcolor{red!30}} &\bfseries{Is the action visible?}{\cellcolor{red!30}}
        & \bfseries{Will the user recognise the action as the right one?}{\cellcolor{red!30}} &\multicolumn{1}{>{\columncolor{red!30}[6pt][0pt]\bfseries}c@{}}{\Centerstack{Will the user understand \\ the feedback?}} \\
        \Xhline{0.25pt}
        \endfirsthead
        \Xhline{1pt}
        % \rowcolor{red!30}
        \multicolumn{1}{c}{\cellcolor{red!30}}
        &\bfseries{Is the effect of the current action the same as the user's goals?} &\bfseries{Is the action visible?}
        & \bfseries{Will the user recognise the action as the right one?} &\multicolumn{1}{>{\bfseries}c@{}}{\Centerstack{Will the user understand \\ the feedback?}} \\
        \Xhline{0.25pt}
        \endhead
        \Xhline{0.25pt}
        \endfoot
        \Xhline{1pt}
        \endlastfoot
        \rowcolor{black}
        \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 1 - access and account set up}} \\
        Heading
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
        \Xhline{0.25pt}
        Heading
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
        \rowcolor{black}
        \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 2 - learning how to map}} \\*
        Heading 
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
        \rowcolor{black}
        \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 3 - contributing data by classifying maps}} \\
        Heading
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
        \Xhline{0.25pt}
        Heading
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
        \Xhline{0.25pt}
        Heading
        & TEXT. 
        & TEXT.   
        & TEXT. 
        & TEXT. \\
    \end{tabularx}%
\end{landscape}
\end{document}

Thanks in advance!

Answer 1

It turns out my original diagnosis, blaming the X column for not being to take an enumerate was not correct. The problem is the ltablex package, and the solution is to issue its directive \keepXColumns. The following document is minimal demonstrating the problem; without the \keepXColumns macro, it produces the missing \item error that you report, with the macro, it compiles fine.

\documentclass{article}

\usepackage{ltablex}
\keepXColumns

\begin{document}

\begin{tabularx}{.9\textwidth}{X}
  \begin{enumerate}
  \item Test.
  \item Test.
  \end{enumerate}
\end{tabularx}

\end{document}

Without \keepXColumns, the package ltablex tries to convert X columns to l columns if there is enough space. This involves the package running some trial code, and that code does not fit well with an enumerate environment in the cell.

Adding \keepXColumns to your posted coded lets it compile fine. However, your code contains many packages loaded twice and is longer than needed. Here is a shorter version:

\documentclass[a4paper,12pt]{article}

\usepackage[main=british]{babel}
\usepackage{graphicx}
\usepackage[table]{xcolor}
\usepackage[section]{placeins}
\usepackage[left=2.5cm, right=2.5cm, top=3.5cm, bottom=3.5cm]{geometry}
\usepackage{titleps,microtype,setspace,amsmath,SIunits,tabularx}
\usepackage{mathptmx}
\usepackage{booktabs,caption,makecell,ltablex}
\usepackage{pdflscape,afterpage}
\onehalfspacing

\renewcommand\theadfont{\small\bfseries}
\renewcommand\tabularxcolumn[1]{m{#1}}
\usepackage[usestackEOL]{stackengine}

\usepackage{enumitem}
\usepackage{etoolbox}
\AtBeginEnvironment{table}{%
    \setlist[enumerate]{nosep,
        topsep     = 0pt,
        partopsep  = 0pt,
        leftmargin = *,
        before     = \vspace{-0.6\baselineskip},
        after      = \vspace{-\baselineskip}
}}

\keepXColumns

\begin{document}

\begin{table}[ht]
  \caption{Cognitive walkthrough goals, tasks and actions}
  \label{table:comparison of techniques}
  \small
  \begin{tabularx}{\linewidth}{@{}
    X
    >{\centering\arraybackslash}X  % content of `X` column is now centered
    X
    @{}}
    \toprule
    \thead{\textbf{Goal}}& \thead{\textbf{Task}} & \thead{\textbf{Action}} \\
    \midrule
    Evaluate the ease in which users can join projects
    &   Access and account set up
    &   \begin{enumerate}
    \item   Teast A: Video provides a powerful way to help you prove your point.

      Test B: Video provides a powerful way to help you prove your point.
    \item Video provides a powerful way to help you prove your point.
    \end{enumerate}     \\
    \addlinespace
    Evaluate the ease in learning to map
    &   Learning how to map
    &   Read tutorial   \\
    \addlinespace
    Contribute data
    &   Contributing data by classifying maps
    &   \begin{enumerate}
    \item Video provides a powerful way to help you prove your point.
    \item Test A: Video provides a powerful way to help you prove your point.

      Test B: Video provides a powerful way to help you prove your point.
    \item Video provides a powerful way to help you prove your point.
    \end{enumerate}     \\
    \addlinespace
    Evaluate if the user likes using the application and whether they like using it
    & -- & --                   \\
    \bottomrule
  \end{tabularx}
\end{table}

\begin{landscape}% Landscape page
  \small
  \setlength\extrarowheight{2pt}
  \begin{tabularx}{\linewidth}{
    >{\columncolor{red!30}} l
    *{3}{X}X@{}
    }\caption{}
    % \label{table:comparison of techniques}
    \\
    \Xhline{1pt}
    \multicolumn{1}{c}{\cellcolor{red!30}}
    &\bfseries{Is the effect of the current action the same as the
    user's goals?}{\cellcolor{red!30}} &\bfseries{Is the action
    visible?}{\cellcolor{red!30}}
    & \bfseries{Will the user recognise the action as the right
    one?}{\cellcolor{red!30}}
    &\multicolumn{1}{>{\columncolor{red!30}[6pt][0pt]\bfseries}c@{}}{\Centerstack{Will
    the user understand \\ the feedback?}} \\
    \Xhline{0.25pt}
    \endfirsthead
    \Xhline{1pt}
    % \rowcolor{red!30}
    \multicolumn{1}{c}{\cellcolor{red!30}}
    &\bfseries{Is the effect of the current action the same as the
    user's goals?} &\bfseries{Is the action visible?}
    & \bfseries{Will the user recognise the action as the right one?}
    &\multicolumn{1}{>{\bfseries}c@{}}{\Centerstack{Will the user
    understand \\ the feedback?}} \\
    \Xhline{0.25pt}
    \endhead
    \Xhline{0.25pt}
    \endfoot
    \Xhline{1pt}
    \endlastfoot
    \rowcolor{black}
    \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 1 - access and
    account set up}} \\
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
    \Xhline{0.25pt}
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
    \rowcolor{black}
    \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 2 - learning how to map}} \\*
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
    \rowcolor{black}
    \multicolumn{5}{l}{\textcolor{white}{\bfseries Task 3 -
    contributing data by classifying maps}} \\
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
    \Xhline{0.25pt}
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
    \Xhline{0.25pt}
    Heading
    & TEXT.
    & TEXT.
    & TEXT.
    & TEXT. \\
  \end{tabularx}
\end{landscape}

\end{document}

• color package removed, already covered by xcolor
• epstopdf package removed, loaded by graphicx if necessary anyway
• [main=british] specification rather than juts [british] for babel
• load geometry, booktabs, caption, makecell, pdflscape, afterpage only once

You should look at using newtxtext and newtxmath instead of mathptmx package; they offer better choices of glyphs with better spacing in mathematics and closer fit to the text fonts, and provide some more flexibility.