"Extra }, or forgotten \endgroup" error in Beamer while using Biber

Question

I've got the following issue using LaTeX Beamer, Biber and AtBeginSection.

Error message:

Error line 30 - ! Extra }, or forgotten \endgroup.<recently read> } \end{frame}
Error line 30 - ! Extra }, or forgotten \endgroup.\endframe ->\egroup\begingroup \def \@currenvir {frame} \end{frame}
Warning line 30 - Font shape `OT1/cmss/m/sc' in size <10.95> not available(Font) Font shape `OT1/cmr/m/sc' tried instead

Input

\documentclass{beamer}

\usepackage[german]{babel}
\usepackage[utf8]{inputenc}
\usepackage{csquotes}

\usepackage[backend=biber]{biblatex}
\addbibresource{../testing/mybib.bib}

\title{Hello}
\date{2022-01-01}
\author{Euclid of Alexandria}

\AtBeginSection{%
    \begin{frame}
        \sectionpage
    \end{frame}
}

\begin{document}

\section{And here we go}

\begin{frame}
Hallo. Hier der Verweis: \cite{khan2020}
\end{frame}

\begin{frame}
    \printbibliography
\end{frame}

\end{document}

mybib.bib

@article{khan2020,
  type = {Article},
  title = {A {{Blockchain-Based Secure Image Encryption Scheme}} for the {{Industrial Internet}} of {{Things}}},
  author = {Khan, Prince Waqas and Byun, Yungcheol},
  year = {2020},
  month = feb,
  journal = {ENTROPY},
  volume = {22},
  number = {2},
  publisher = {{MDPI}},
  address = {{ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND}},
  doi = {10.3390/e22020175},
  abstract = {...}
}

I can avoid the error by

--> Commenting out the \begin{frame} and \end{frame} command in the AtBeginSection part which unfortunately breaks my layout because no frame is drawn otherwise. (I use this command as described in the Beamer User Guide Section 10.2):

\AtBeginSection{%
    %\begin{frame}
        \sectionpage
    %\end{frame}
}

--> Commenting out the \printbibliography which leads to a missing bibliography:

\begin{frame}
%   \printbibliography
\end{frame}

I really don't understand what's going on there so any help is very much appreciated.

Side note I configured my TexMaker for Biber in MacOS as described in this post: Biblatex with Biber: Configuring my editor to avoid undefined citations

Answer 1

The problem is that biblatex tries to insert the bibliography as a new section. As this happens within a frame, this would nest the section page frame within another frame, which is not allowed.

You can avoid the problem by using \printbibliography[heading=none]:

\documentclass{beamer}

\usepackage[german]{babel}
\usepackage[utf8]{inputenc}
\usepackage{csquotes}

\usepackage[backend=biber]{biblatex}

\addbibresource{biblatex-examples.bib}

\title{Hello}
\date{2022-01-01}
\author{Euclid of Alexandria}

\AtBeginSection{%
    \begin{frame}
        \sectionpage
    \end{frame}
}

\begin{document}

\section{And here we go}

\begin{frame}
Hallo. Hier der Verweis: \cite{knuth:ct}
\end{frame}

\begin{frame}
    \printbibliography[heading=none]
\end{frame}

\end{document}

---

Or you could redefine the bib heading. This way you would automatically get a frametitle:

\documentclass{beamer}

\usepackage[german]{babel}
\usepackage[utf8]{inputenc}
\usepackage{csquotes}

\usepackage[backend=biber]{biblatex}

\addbibresource{biblatex-examples.bib}

\defbibheading{bibliography}[\refname]{%
  \frametitle{#1}%
}

\title{Hello}
\date{2022-01-01}
\author{Euclid of Alexandria}

\AtBeginSection{%
    \begin{frame}
        \sectionpage
    \end{frame}
}

\begin{document}

\section{And here we go}

\begin{frame}
Hallo. Hier der Verweis: \cite{knuth:ct}
\end{frame}

\begin{frame}
    \printbibliography
\end{frame}

\end{document}