Unicode-math: subscripts work with Bitstream Vera Sans, but not with DejaVu Sans

I'm trying to typeset some slides with text in either Bitstream Vera Sans or DejaVu Sans and maths in Fira Math using LuaLaTeX and unicode-math. When using Bitstream Vera Sans, everything works fine (except for the many glyphs missing in Fira Math):

When using DejaVu Sans, on the other hand, subscripts don't:

What could be the cause of the difference?

\documentclass{minimal}
\usepackage{unicode-math}
\setmathfont{Fira Math}
% \setmathfont[range=up/{latin,Latin}]{Bitstream Vera Sans}
% \setmathfont[range=it/{latin,Latin}]{Bitstream Vera Sans Oblique}
\setmathfont[range=up/{latin,Latin}]{DejaVu Sans}
\setmathfont[range=it/{latin,Latin}]{DejaVu Sans Oblique}
\begin{document}
$a_i$
\end{document}

• looks okay here. Is your system up-to-date? – Ulrike Fischer Oct 24 '20 at 21:35
• TeXLive 2020, as packaged by Norbert for Debian Unstable. – jch Oct 24 '20 at 21:41
• I can’t reproduce the bug on my own box. What version of DejaVuSans.ttf does otfinfo -i report? – Davislor Oct 24 '20 at 22:08
• Version 2.37 (for both the regular and oblique variants). As an additional element, the issue doesn't occur if I remove the up substitution, even though the up shapes are not used in the sample document. – jch Oct 24 '20 at 22:10