An issue with current TeXLive (scrartcl?)

[Angelo Graziosi]

After updating TeXLive, the following STC, created from a more complex document, does not build any more:

---------------------
$ cat test.tex
\documentclass{scrartcl}

\newcommand{\RomanNumeralCaps}[1]{\MakeUppercase{\romannumeral #1}}

\begin{document}
hello! \RomanNumeralCaps{5}
\end{document}

$ pdflatex test.tex
[...]
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrartcl.cls
Document Class: scrartcl 2022/07/04 v3.37 KOMA-Script document class (article)
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrkbase.sty
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrbase.sty
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrlfile.sty
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrlfile-hook.sty
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrlogo.sty)))
(/LocalApps/texlive/texmf-dist/tex/latex/graphics/keyval.sty)))
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/tocbasic.sty)
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/scrsize11pt.clo)
(/LocalApps/texlive/texmf-dist/tex/latex/koma-script/typearea.sty))
(/LocalApps/texlive/texmf-dist/tex/latex/l3backend/l3backend-pdftex.def)
No file test.aux.
---------------------

Here it hangs. After CTRL-C it prints:

---------------------
\__text_expand_loop:w ..._text_expand_space:w }}#1
                                                  \q__text_recursion_stop
l.8 hello! \RomanNumeralCaps{5}

?
---------------------

Changing the newcommand to

\newcommand{\RomanNumeralCaps}[1]{#1}

it builds. The last time I have built the full document was on may 31, 2022 (about two months ago).