Tikz/pgfplots include .csv file in pgfplotstableread

Question

I'm trying to make a 3D-histogram based on the example shown here. However, there are two things I can't figure out on my own, as I'm still learning to use the Tikz/pgf packages.

1. When I try to include csv data from a seperate file (i.e. uncommenting 'paperYearData.csv' (line 65) and commenting the data below (lines 66-82)), instead of writing it in main.tex, I get the following errors:

I did search online of course and tried a few things, but I could not resolve this problem. Most people use \addplot to include the csv file, but in this case we're using pgfplotstableread. I would like to have the csv file seperately, as it will be a lot of data. Anyone any suggestions?

2. When I change 'ymin=1999' (line 120) to something like 'ymin=2005', I get the following errors:

What is going on here? It seems as if delta y is getting too 'small' (read: order of 10), some value gets too big somewhere. Everything seems to compile but I still get this error.

I'm using Overleaf.

I would really appreciate any help. Thank you in advance.

Best regards, Thomas

Please find below a MWE:

main.tex

\documentclass{article}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{calc}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
% 3D-histogram: https://tex.stackexchange.com/questions/491565/3d-histogram-bar-chart
\pgfplotsset{compat=1.16}
% from https://tex.stackexchange.com/a/102770/121799
\def\pgfplotsinvokeiflessthan#1#2#3#4{%
    \pgfkeysvalueof{/pgfplots/iflessthan/.@cmd}{#1}{#2}{#3}{#4}\pgfeov
}%
\def\pgfplotsmulticmpthree#1#2#3#4#5#6\do#7#8{%
    \pgfplotsset{float <}%
    \pgfplotsinvokeiflessthan{#1}{#4}{%
        % first key <:
        #7%
    }{%
        \pgfplotsinvokeiflessthan{#4}{#1}{%
            % first key >:
            #8%
        }{%
            % first key ==:
            \pgfplotsset{float <}%
            \pgfplotsinvokeiflessthan{#2}{#5}{%
                % second key <
                #7%
            }{%
                \pgfplotsinvokeiflessthan{#5}{#2}{%
                    % second key >
                    #8%
                }{%
                    % second key ==
                    \pgfplotsset{float <}%
                    \pgfplotsinvokeiflessthan{#3}{#6}{%
                        % third key <
                        #7%
                    }{%
                        % third key >=
                        #8%
                    }%
                }%
            }%
        }%
    }%
}%
\begin{document}
\ifdefined\gconv
\else
    \pgfmathsetmacro{\gconv}{0.1}
\fi
\newcommand\maxZValue{10} % manually change this value to max z value in dataset!
\pgfplotstableread[col sep=comma,header=true]{%
    % paperYearData.csv
    x,y,myvalue
    1,2001,5
    1,2005,3
    1,2009,1
    1,2010,4
    2,2004,5
    2,2005,3
    3,2010,1
    3,2011,4
    4,2002,5
    4,2005,3
    5,2011,1
    6,2012,6
    6,2015,6
    6,2017,6
    6,2018,6
    6,2020,4
}{\datatable}
\pgfplotstablesort[create on use/sortkey/.style={
    create col/assign/.code={%
        \edef\entry{{\thisrow{x}}{\thisrow{y}}{\thisrow{myvalue}}}%
        \pgfkeyslet{/pgfplots/table/create col/next content}\entry
    }
},
sort key=sortkey,
sort cmp={%
    iflessthan/.code args={#1#2#3#4}{%
        \edef\temp{#1#2}%
        \expandafter\pgfplotsmulticmpthree\temp\do{#3}{#4}%
    },
},
sort,
columns/Mtx/.style={string type},
columns/Kind/.style={string type},]\resulttable

{\datatable}
\begin{figure}[ht]
    \centering
    {
    \small
\begin{tikzpicture}%[x={(0.866cm,-0.5cm)},y={(0.866cm,0.5cm)},z={(0cm,1 cm)}]
    \pgfplotsset{set layers}
    \begin{axis}[% from section 4.6.4 of the pgfplotsmanual
        view={165}{50},
        width=\linewidth, % was: 440pt
        height=380pt, % was: 380pt
        z buffer=none,
        title={3D-histogram},
        xmin=0,xmax=6,
        ymin=1999,ymax=2022,
        zmin=0,zmax=\maxZValue*2,
        enlargelimits=upper,
        ztick={0,1/4*\maxZValue*2,2/4*\maxZValue*2,3/4*\maxZValue*2,\maxZValue*2},
        zticklabels={0,\pgfmathparse{1/4*\maxZValue}\pgfmathresult,\pgfmathparse{2/4*\maxZValue}\pgfmathresult,\pgfmathparse{3/4*\maxZValue}\pgfmathresult,\maxZValue}, % here one has to &quot;cheat&quot;
        % meaning that one has to put labels which are the actual value 
        % divided by 2. This is because the bars will be centered at these
        % values
        xtick=data,
        xticklabels={Industrial,Tendon,Origami,Metamaterial,Linkage,Compliant},
        extra tick style={grid=major},
        ytick=data,
        grid=major, %changes lines on axes (was: minor)
        major grid style={gray!60},
        xlabel={$Category$},
        ylabel={$Year$},
        zlabel={$Amount~of~papers$},
        z tick label style={
            anchor=east}, % used to align label with axis line
        y tick label style={
            anchor=east},
        minor tick num=1,
        point meta=explicit,
         % define the custom colormap. from: https://tex.stackexchange.com/questions/370960/custom-colorbar-not-showing-colors-correctly/370962
        colormap={my colormap}{
            rgb=(0.59, 0.29, 0.0),
            rgb=(1, 0, 0),
            rgb=(0, 0, 1),
            rgb=(1, 1, 0),
            rgb=(0, 0.5, 0.5),
            rgb=(0, 1, 0),
        },
        % colormap name=viridis,
        scatter/use mapped color={
            % fill=blue!70!black,fill opacity=.1
            draw=black,fill=mapped color!80,fill opacity=.8
            % \definecolorseries{test}{rgb}{step}[rgb]{.95,.85,.55}{.17,.47,.37}
            % \resetcolorseries{test}
        },
        execute at begin plot={}
        % legend cell align = left,
        % legend style={draw=none},
        % \legend{test,yeah,234,21,213,2153},
        % legend style={at={(0.03,0.97)}, anchor=north west, legend cell align=left,align=left,draw=mapped color!80}
    ]
        % \legend{empirical,lognormal fit}
        % \addlegendentry{Linkage}
        % \addlegendentry{Metamaterials},
        \path let \p1=($(axis cs:0,0,1)-(axis cs:0,0,0)$) in 
        \pgfextra{\pgfmathsetmacro{\conv}{2*\y1}

        \ifx\gconv\conv
        \else
            \xdef\gconv{\conv}
            \typeout{Please\space recompile\space the\space file!}
        \fi     
        };
        \path let \p1=($(axis cs:1,0,0)-(axis cs:0,0,0)$) in 
        \pgfextra{\pgfmathsetmacro{\convx}{veclen(\x1,\y1)}
        \typeout{One\space unit\space in\space x\space direction\space is\space\convx pt}
        };                  
        \path let \p1=($(axis cs:0,1,0)-(axis cs:0,0,0)$) in 
        \pgfextra{\pgfmathsetmacro{\convy}{veclen(\x1,\y1)}
        \typeout{One\space unit\space in\space y\space direction\space is\space\convy pt}
        };                  
        \addplot3 [visualization depends on={\gconv*z \as \myz}, % you may have to recompile to get the prefactor right
        scatter/@pre marker code/.append style={/pgfplots/cube/size z=\myz},%
        scatter/@pre marker code/.append style={/pgfplots/cube/size x=6pt},% used to be: x=11.66135pt
        scatter/@pre marker code/.append style={/pgfplots/cube/size y=6pt},% used to be: y=9.10493pt
        scatter,only marks,
        mark=cube*,mark size=5,opacity=1]
        table[x expr={\thisrow{x}},y expr={\thisrow{y}},z
        expr={1*\thisrow{myvalue}},
        meta expr={-1*\thisrow{x}}
        ] \resulttable;
    \end{axis}

    \makeatletter
        \immediate\write\@mainaux{\xdef\string\gconv{\gconv}\relax}
    \makeatother
\end{tikzpicture}
}

\caption{This is a test caption.}
\label{fig:testlabel}
\end{figure}

\end{document}

paperYearData.csv

x,y,myvalue
1,2001,5
1,2005,3
1,2009,1
1,2010,4
2,2004,5
2,2005,3
3,2010,1
3,2011,4
4,2002,5
4,2005,3
5,2011,1
6,2012,6
6,2015,6
6,2017,6
6,2018,6
6,2020,4