slur moves on its own (in specific situations)

[Mark Polesky]

Hey guys,

I found another head-scratcher bug...  This is the sort of thing
you can only find by accident.  The first measure contains two
identical halves; the slur in the first half is printed properly,
but the slur in the second half is printed too high above the
beam.

I honestly tried to make this example file as tiny as possible,
but the combination of elements needed to trigger the bug seems
curiously specific.  For example, if I remove any one of these
elements, the problem disappears:

#(set-default-paper-size "letter")
#(set-global-staff-size 17)
left-margin = 0.75\in  --and--  right-margin = 0.75\in
\key bf \major
\break

Stranger still, if I change staff-size to 15, 16, 18, 19, or 20,
the problem goes away, and if I change both margins to 0.5\in or
1\in, the problem also goes away.

So, what's going on?  This is bizarre...

Thanks.
- Mark


* * * * * * * * * * * * * * * *


\version "2.14.0"

#(set-default-paper-size "letter")
#(set-global-staff-size 17)

\paper {
  left-margin = 0.75\in
  right-margin = 0.75\in
}

\relative bes' {
  \key bes \major
  <<
    { bes='4 f8 f16( f-.) bes4 f8 f16( f-.) | }
    \\
    { d='8 d4 d16 r d8 d4 d16 r | }
    \\
    { d='8 d16 f s4 d8 d16 f s4 | }
  >>
  \break
  bes4 r2. |
}