Dotted note in Tuplet

[arshiacont]

The second note in this excerpt (courtesy of Beethoven!) is marked as dotted but not come out as such when rendered. Am I doing anything wrong?

{[ \stemsUp \tuplet<"">(d/12 d2/12. c/24)
 \stemsDown \tuplet<"", dispNote="/8">( c/12 b1/12 a/12)
 \stemsUp  \beamsOff a/4 \beamBegin:1 g/8  g/8 \beamEnd:1  
 ]
  }

[dfober]

actually, writing d2/12. is equivalent to d2/8, that's why the dot is no present.
You have to force the note appearance using \displayDuration i.e.

\tuplet<"">(d/12 \displayDuration<1, 8, 1>(d2/12.) c/24)

I know that's not very convenient in such an obvious case. The problem is not simple to solve and contextual information is missing to fix it. I leave this issue opened and see what I can do.