\version "2.23.10"

music = \relative g' {
  \time 6/8
  \partial 8
  r8 |
  \repeat volta 2 {
    g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 |
    g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 |
    %g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 |
    %g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 | g8 r8 r8 d8 r8 r8 |
    \alternative {
      \volta 1 { g8 r8 r8 d8 r8 r8 }
      \volta 2 { g8 r8 r8 g,8 r8 }
    }
  }
  \bar "|."
}

\markup "This is how it is supposed to look like..."
\score {
  \music
}


musicb = \relative g' {
  \time 6/8
  \partial 8
  r8 |
  \repeat volta 2 {
    \repeat unfold 8 { g8 r8 r8 d8 r8 r8 }
    \alternative {
      \volta 1 { g8 r8 r8 d8 r8 r8 }
      \volta 2 { g8 r8 r8 g,8 r8 }
    }
  }
  \bar "|."
}

\markup "...and this IMO is a bug in bar 4"
\score {
  \musicb
}