space char lost between two writes

[u-fischer]

\DocumentMetadata
  {
    tagging=on,
    uncompress
  }
\documentclass{article}
\makeindex
\begin{document}
\showoutput
aaa\index{aaa} \index{bbb}bbb 
\end{document}

gives <001C001C001C>-333<002300230023> in the stream

[FrankMittelbach]

with lualatex (not with pdftex)