Why does this pdf figure crash lualatex?

I have an old workflow that uses LaTeX itself to process diagrams and plots. I've used this generate hundreds of figures over the years. This has suddenly started producing invalid pdf figure files: they won't open in Acrobat (though they do open in SumatraPDF); including them in a document causes luatex to output several warning messages (invalid compressed object) and a corrupt final file. Strangely, they do seem to work with pdftex.

Compiling this document with lualatex is enough to trigger the problem on my machine.

\documentclass{article}
\usepackage{graphicx}
\begin{document}
\includegraphics[width=\textwidth]{embed.pdf}
\end{document}

Here is embed.pdf

The figure was initially generated by gnuplot, using the following:

set term postscript eps mono
set output "fig.eps"
plot x**2 title "AAA"

I then created a version with a Greek letter by compiling this document (embed.tex) using latex+dvips

\documentclass{article}
\usepackage{graphicx}
\usepackage{psfrag}
\pagestyle{empty}
\begin{document}
\psfrag{AAA}{\(\alpha\)}
\includegraphics{fig.eps}
\end{document}

Finally, I did

ps2eps --ignoreBB embed.ps
epstopdf embed.eps

to create the pdf figure. Converting embed.eps to pdf using cloudconvert.com does seem to work, so I think the problem is caused by either epstopdf or ghostscript. What's going on here?

I think this old question is probably related, but there is no example pdf file so it's impossible to be sure.

EDIT

It seems increasingly likely that something is going wrong at the very last step (eps2pdf conversion). Here is the eps file that is being converted: embed.eps. What's not clear is whether the issue is limited to my own machine (running texlive 2025 under cygwin).