Part of staff does not obey alignAboveContext

[Davide Liessi]

Dear all,

in the second example below, the second part of the ossia staff jumps
below the main staff.
Am I doing something wrong or is it a bug in LilyPond?

Best wishes.
Davide

%%%%%

\version "2.23.4"

\score {
  \new Staff = "main" <<
    \new Voice {
      <<
        { a'8 }
        \new Staff = "ossia"
        \with { alignAboveContext = "main" }
        { a'8 \stopStaff }
      >>
      a'8 a'8 a'8 a'2
      <<
        { a'1 }
        \context Staff = "ossia"
        { \startStaff a'1 }
      >>
    }
  >>
}

\score {
  \new Staff = "main" <<
    \new Voice {
      <<
        { a'8 a'8 }
        \new Staff = "ossia"
        \with { alignAboveContext = "main" }
        { a'4 \stopStaff }
      >>
      a'8 a'8 a'2
      <<
        { a'1 }
        \context Staff = "ossia"
        { \startStaff a'1 }
      >>
    }
  >>
}