Die Lösung ist die richtige Verwendung der Umgebung für longtable:
%% #1 Number of columns
%% #2 Column definitions
%% #3 Header
%% #4 Caption im TOC
%% #5 Caption
%% #6 Label
\newenvironment{MyLongTable}[6]{%
\begin{longtabu} to \textwidth {#2}%
%---------- Table head on first page ----------
\caption[#4]{#5\label{#6}}\\
\toprule
#3\\
\midrule
\endfirsthead
%
%---------- Table head on other pages ----------
\caption[]{(Fortsetzung)}\\
\multicolumn{#1}{l}{\tiny ...continued from previous page...}\\
\toprule
#3\\
\midrule
\endhead
%
%---------- Table footer ----------
\hline
\multicolumn{#1}{r}{\tiny ...continue on next page...}\\
\endfoot
%
%---------- Table footer on last page ----------
\bottomrule
\endlastfoot
}{\end{longtabu}}
%%%%%%%%%%%%%%%%%%%%%
% package: tcolorbox
%%%%%%%%%%%%%%%%%%%%%
\newtcolorbox{infobox}{
title={Infobox},
colback=red!5!white,
colframe=red!75!black
} }{\end{longtabu}}
