The following first reported at the unicode-math github https://github.com/wspr/unicode-math/issues/383 but the problem can be seem with plain tex.
In the tex below there are six repeated instances of a subscripted bracket they should all be the same but the first one is misaligned. It appears to be a misbehaviour of \mathchoice as if I change the size of the scriptscript font the effect changes, even though there is no visible script script text. The attached images show the output with the file as below and with the scriptscript font changed to at 25pt I've tried it with fam 0,1,2 all set up as the same font, or as here with just fam0 using a opentype font. David \font\m= "[latinmodern-math.otf]/OT:script=math;language=DFLT;" at 10pt \font\sm= "[latinmodern-math.otf]/OT:script=math;language=DFLT;" at 7pt \font\ssm= "[latinmodern-math.otf]/OT:script=math;language=DFLT;" at 5pt \textfont0=\m \scriptfont0=\sm \scriptscriptfont0=\ssm \Umathcode`.= 0 0 `. \hrule $$ \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} $$ \hrule $$ \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} \hbox{$\left)\vbox to15pt{}\right.$}_{\smash.} $$ \hrule \bye
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