Line-breaking with non-aligned barlines

[David Sumbler]

Below I have shown a compile-able 93 lines (sorry it can't be made much
shorter) from the files for a much longer piece.

In this particular passage the harpsichord plays 4 bars in strict tempo
whilst the flute plays 4 bars rubato.  (The 2 lines do not fit and are
meant to sound terrible together!)

After much effort I have managed to get a layout in the score which
mimics the original manuscript, but there is one problem I cannot
solve.  Although these 4 bars can just about be made to fit on to one
line, there actually needs to be a page break at some point.  This is
because there is a narrator who has a short speech during the pause at
the end of the extract.  This will require an inch or two of horizontal
space, and the 4 bars in question will then be too compressed.  The
page break should come at the end of one of the harpsichord's bars,
which correspond to the bars in the rest of the orchestra.  (I have
only included 1 violin line here; none of the other instruments play
during the 4 bars in question.)

Unfortunately, every time I ask for a \break Lilypond gives me the
dreaded

"warning: forced break was overridden by some other event, should you
be using bar checks?"

I have looked at the Lilypond Snippet "Printing music with different
time signatures [0.35714]" as well as another relevant snippet, and
have compiled it successfully.  The line break works as expected.  Yet
my code produces the warning and refuses to make a line break.

What have I missed?

David

%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.19.81"

\language "english"

#(set-global-staff-size 16)

gliss = \markup { \larger \italic "gliss." }

FifteenFlute = {
  <<
    { \relative {
      R1 | R1\fermataMarkup |
        \override Staff.TimeSignature.stencil = ##f
        \time 25/16
        \scaleDurations 8/4 { bf''8[(\mf a16]) r }
        \scaleDurations 7/4 { bf8[( a16]) r }
        \scaleDurations 6/4 { bf8[( a16]) r }
        bf8[( a16]) r 
        \time 4/4
        \tuplet 5/4 { bf8( c df ef e } fs2 
        \time 7/8
        \scaleDurations 7/8 { e4 ds cs bs) } 
        \time 9/16
        R1*9/16\fermataMarkup 
        \time 4/4
    } }
  >>
}

ScoreFifteenFirstViolinA = {
  <<
    { \relative {
      d'8(\p\>\glissando^\gliss g)\! r4
      \override DynamicText.X-offset = #-2
      g8(\mp\>\glissando^\gliss b)\! r4 |
      b8(\mf\>\glissando^\gliss d)\! r4
      \revert DynamicText.X-offset
      d8(\f\>\glissando^\gliss e)\! r4\fermata |
      R1*3 | R1\fermataMarkup |
    } }
  >>
}

FifteenHarpsUpper = {
  <<
    { \relative {
      R1 | R1\fermataMarkup |
      \key a \major
      a''16\mf \repeat unfold 9 { gs a } b bs cs d ds e cs a e cs e gs a |
      \repeat unfold 9 { b as } b cs ds e b gs e8 r \acciaccatura ds' e 
r\fermata |
    } }
  >>
}

FifteenHarpsLower = {
  <<
    \clef bass
    { \relative {
       R1 | R1\fermataMarkup |
      \key a \major
      \clef treble
      \repeat unfold 4 { a16 e' cs e a e cs e } | \repeat unfold 2 { a, fs' d 
fs a fs d fs } |
      gs, e' d e gs e d e gs,8 r \clef bass \acciaccatura ds e r\fermata |
     } }
  >>
}

\score {
  <<
    \new Staff \with { instrumentName = "Flute" } \FifteenFlute
    \new PianoStaff \with { instrumentName = "Harpsichord" } <<
      \new Staff \FifteenHarpsUpper
      \new Staff \FifteenHarpsLower >>
    \new Staff \with { instrumentName = "Violins I" } \ScoreFifteenFirstViolinA 
  >>
  \layout {
   \context { \Score
              \remove "Timing_translator"
              \remove "Default_bar_line_engraver"
            }
   \context {
     \Staff
     \consists "Timing_translator"
     \consists "Default_bar_line_engraver"
   }
   \context {
     \Voice
     \remove "Forbid_line_break_engraver"
   }
   indent = 26\mm
 }
}
%%%%%%%%%%%%%%%%%%%%%%%%