View difference between Paste ID: k0MdqC0p and wDM2jiTS

 \documentclass{scrartcl}
 \usepackage{beamerarticle}
 %\documentclass{beamer}
 
 \usepackage[utf8]{inputenc}
 
 \setbeamertemplate{footline}[frame number]
 
 \mode<article>{
     \renewcommand{\frametitle}[1]{\subsubsection*{#1 [Slide \insertframenumber]}}
     \def\insertsection{}
 }
 
 \mode<article>
 \usepackage{xparse}
 \makeatletter
 \expandafter\let\expandafter\originalsection\expandafter=\csname @orig\string\section\endcsname
-\RenewDocumentCommand{\section}{ d<> s o m }
+\RenewDocumentCommand{\section}{ D<>{} s o m }
 {
   \alt<#1>
   {
     \IfBooleanTF {#2}
     {
       \originalsection*{#4}
       %\beamer@atbeginsections % breaks because section* is also used e.g. in the TOC
     }
     {
       \IfNoValueTF {#3} { \originalsection{#4} } { \originalsection[#3]{#4} }
       \beamer@atbeginsection
     }
   }
   {
     \beamer@secgobble
   }
 }
 \makeatother
 \mode<all>
 
 \AtBeginSection[]
 {
     \begin{frame}<article:0>
         \begin{center}
             \structure{\Huge \insertsection}
         \end{center}
     \end{frame}
 }
 
 \begin{document}
 
     \begin{frame}
         \tableofcontents
     \end{frame}
 
     \section{Section 1}
 
         \begin{frame}
             \frametitle{Frame A}
 
             Frame A
         \end{frame}
 
     \section{Section 2}
     %\section*{Section Star}
 
         \begin{frame}
             \frametitle{Frame B}
 
             Frame B
         \end{frame}
 
 \end{document}