Weird vertical spacing bug in lyrics

[Mats Bengtsson]

   Hi,

   In the following example, I get a weird extra spacing between the first
   and second line of lyrics. I've tried to reduce the example as much as
   possible and if I for example change the clef of the melody line to
   regular treble clef, or remove the introductory six bars or remove the
   last line of lyrics, the spacing is normal again. It's a regression
   compared to version 2.22.2, or if it's a Heisen-bug it's not triggered
   in 2.22.2.

   (If you think the first bars of music look weird, it's since it's
   notated for "scordatura", i.e. re-tuned violin).

   \version "2.23.13"
   vi = \relative c''' {
   \time 4/4
   g8. b,16 8. e16 8. fis,16 8 8 |
   c''8. a,16 b8. e16 f8. g16 e4 |
   g8. b,16 8. e16 8. fis,16 8 8 |
   e'8. fis16 g8 a16 g fis8. e16 e4 |
   g8. a,16 e'8. a16 fis4 r |
   r8 b!16 g c8 e, b8. a16 8 8 |
   \bar "||"
   }
   song = \relative c'' {
   \key f \major
   \time 4/4
   R\breve*3 |
   \bar "||"
   \repeat volta 2 {
   b8. fis16 8. g16 8. d16 8 8 |
   d'8. d,16 e8. fis16 g8. a16 fis4 }
   }
   lIa = \lyricmode{
   \set stanza =  "1. "
   Süs -- ses Kind/ der Vä -- ter hof -- fen!
   Kind der Men -- schen Lö -- se -- geld:
   Hey -- land wirst -- tu nun ge -- bo -- ren/
   Zu er -- ret -- ten/ was verl -- oh -- ren?
   }
   lIb = \lyricmode{
   Steht der Him -- mel nun -- mehr of -- fen?
   Lie -- fert Gott dich jetzt der Welt?
   }
   lIIa = \lyricmode{
   \set stanza =  "2. "
   Eh die Welt die Zeit ge -- ken -- net/
   GOtt Ihm e -- wig gleich ge -- bahr:
   GOtt/ das Wort kömpt auff die Er -- den/ Wun -- der!
   GOtt sol Fleisch hier wer -- den!
   }
   lIIb = \lyricmode{
   Ein -- en Sohn/ das Wort ge -- nen -- net/
   Das im An -- fang war/ und wahr;
   }
   lIIIa = \lyricmode{
   \set stanza =  "3. "
   Hei -- lig -- keit der höch -- sten Gü -- te!
   Ach! ver -- läst du dei -- nen Thron!
   Den nichts/ was er schuff/ kan schlis -- sen/
   Kan die zar -- te Jung -- fer küs -- sen.
   }
   lIIIb = \lyricmode{
   Wie ent -- setzt sich mein Ge -- mü -- the!
   Wird Gott ei -- nes Men -- schen Sohn?
   }
   bc = \relative c {
   \clef bass
   \time 4/4
   g4 d' g, b b a fis g |
   g d' g, b g e fis b |
   g gis a ais b g d' d, |
   \bar "||" \break
   \repeat volta 2 {
   g' d e b |
   fis' e cis d |}
   }
   \score{
     \new StaffGroup <<
       \new Staff \vi
       \new Staff \new Voice=mel {\clef soprano \song }
       \new Lyrics \lyricsto mel \lIa
       \new Lyrics \lyricsto mel \lIb
       \new Lyrics \lyricsto mel \lIIa
       \new Lyrics \lyricsto mel \lIIb
       \new Lyrics \lyricsto mel \lIIIa
       \new Lyrics \lyricsto mel \lIIIb
       \new Staff \bc
     >>
   }
      /Mats