Conflict between babel and graphicx (Tex Live 2019/Debian)

Question

I have a very strange behavior with the following code

\documentclass{article}
\usepackage[ngerman]{babel}
\usepackage{graphicx}

\begin{document}

\begin{figure}[htb]
  \centering \includegraphics[width=.5\textwidth]{normal_dichte}
  \caption{Dichten von Normalverteilungen} \label{fig:normal}
\end{figure}
\begin{figure}[htb]
  \centering  \includegraphics[width=.5\textwidth]{exponential_dichte}
  \caption{Dichten von Exponentialverteilungen}\label{fig:exponential}
\end{figure}
\begin{figure}[htb]
  \centering  \includegraphics[width=.5\textwidth]{chi_3}
  \caption{Dichten einer $\chi^2$-Verteilung}\label{fig:chi}
\end{figure}
Abbildungen~\ref{fig:normal},~\ref{fig:exponential} und~\ref{fig:chi}.
\end{document}

When I compile this, the third picture is not included, and \ref{fig:chi} is reported as an undefined reference. I get the following output:

Running `LaTeX' on `problem2' with ``pdflatex -synctex=1  -file-line-error    problem2.tex'' 
This is pdfTeX, Version 3.14159265-2.6-1.40.20 (TeX Live 2019/Debian) (preloaded format=pdflatex)
 restricted \write18 enabled.
entering extended mode
(./problem2.tex
LaTeX2e <2020-02-02> patch level 2
L3 programming layer <2020-02-14>
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2019/12/20 v1.4l Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
(/usr/share/texlive/texmf-dist/tex/generic/babel/babel.sty
(/usr/share/texlive/texmf-dist/tex/generic/babel/switch.def)
(/usr/share/texlive/texmf-dist/tex/generic/babel-german/ngerman.ldf
(/usr/share/texlive/texmf-dist/tex/generic/babel-german/ngermanb.ldf
(/usr/share/texlive/texmf-dist/tex/generic/babel/babel.def
(/usr/share/texlive/texmf-dist/tex/generic/babel/txtbabel.def)))))
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphicx.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/share/texlive/texmf-dist/tex/latex/graphics-cfg/graphics.cfg)
(/usr/share/texlive/texmf-dist/tex/latex/graphics-def/pdftex.def)))
(/usr/share/texlive/texmf-dist/tex/latex/l3backend/l3backend-pdfmode.def)
(./problem2.aux)
(/usr/share/texlive/texmf-dist/tex/context/base/mkii/supp-pdf.mkii
[Loading MPS to PDF converter (version 2006.09.02).]
) (/usr/share/texlive/texmf-dist/tex/latex/epstopdf-pkg/epstopdf-base.sty
(/usr/share/texlive/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))

LaTeX Warning: Reference `fig:chi' on page 1 undefined on input line 19.

[1{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map} <./normal_dichte.png> <./
exponential_dichte.png>] [2]
Overfull \vbox (10.0pt too high) has occurred while \output is active
(./problem2.aux)

LaTeX Warning: There were undefined references.

The problem goes away if I do any one of the following three things:

1. Comment out \usepackage[ngerman]{babel}. The first two pictures are on page 1, and the third picture is on page 2, and there is no problem with the references.
2. Reduce the widths to .4\textwidth. Then all three pictures fit on one page and the problem disappears.
3. I also tried Tex Live 2021 on Overleaf, and there the original code compiles just fine.

Is there a way to get the original code to work without changing my Tex Live version?