`a` and `\symnormal{a}` make differrent result

[FlatLanguage]

Description

When set font with range option, \symnormal{a} follows this setting, but behavior of a is strange.

Minimal example demonstrating the issue

\documentclass{article}

\usepackage{amsmath, unicode-math}

\setmathfont{latinmodern-math.otf}
\setmathfont[range={`𝜕}]{STIXTwoMath-Regular.otf}
\setmathfont[range={`𝑎}]{FiraMath-Regular.otf}

\begin{document}
\[a\symnormal{a}\partial\symnormal{\partial}\]
\end{document}

\documentclass{article}

\usepackage{amsmath, unicode-math}

\setmathfont{latinmodern-math}
\setmathfont[range={`∂, `𝜕}]{STIXTwoMath-Regular}
\setmathfont[range={`a, `𝑎}]{FiraMath-Regular}

\begin{document}
\[a\symnormal{a}\partial\symnormal{\partial}\]
\end{document}