Progress bar not working correctly with `\tikzexternalize`

[gjkf]

Externalizing Tikz pictures for faster compile time breaks the progress bar. Consider the following MWE

\documentclass[usenames,dvpinames,mathserif]{beamer}
\usepackage{tikz}
\tikzsetexternalprefix{figures/}
\tikzexternalize%
\usepackage{pgfplots}
\pgfplotsset{compat=1.14,cycle list=pgfplotsthemetol}

\title[Composizione Tipografica]{Storia della composizione tipografica di simboli matematici}
\subtitle{Da Monotype a \LaTeX}
\author{Davide Cossu}
\institute{Liceo Scientifico Giovanni Marinelli}
\date{A.S. 2018}
\subject{Composizione tipografica}
\keywords{tipografia,storia,composizione tipografica}

\usetheme[progressbar=head]{metropolis}

\begin{document}
\section{One}
\begin{frame}[c]{Ttitle1}
  Test
\end{frame}
\section{Two}
\begin{frame}[c]{Title2}
  Test 2
\end{frame}
\end{document}

This compiles fine but the progress bar will not be of the correct length, instead it will advance of a fixed distance, reaching 100% after many, many slides. Simply removing the \tikzexternalize command fixes it.

You can see here the problem. Removing the command yields this:

There must be some sort of incompatibility between externalization and the progress bar since other figures work just fine.

[jakobmoss]

Are you using the theme version shipped with TeXlive or the one from this GitHub repo? Because the externalization (issue #260 ) was fixed after the most recent release. I had similar progress bar issues (however on the section pages). Using the newer packages from GitHub solved them for me.

[gjkf]

I was using TeXLive's version, yes. I guess that solves it, thanks for the reference. Guess we can close this.