programming error: no solution found for Bezier intersection

[Federico Bruni]

Hi

I have a real piece where I get the following error (printed 6 times):
programming error: no solution found for Bezier intersection
continuing, cross fingers

The PDF looks fine, but I'd like to avoid this error in the logs, if 
possible.

By commenting some code I found, by trial and error, the bar which 
triggers the error.
However, if I move that bar in a minimal example, I don't get the error.
I tried to copy every setting from the real file (even if probably 
unrelated), but cannot reproduce it.
Perhaps it depends on page layout?!?

In the archives I found some discussion on this programming error, but 
it was triggered by fingerings (not present in my example):
https://lists.gnu.org/archive/html/lilypond-user/2011-09/msg00191.html

Thanks
Federico

\version "2.19.48"

global = {
 \key g \major
 \time 4/4
}

upper = \relative {
 \global
 g'16( a g e) d( e\2 d b) a( ais a g) r4 |
}

lower = \relative {
 \global
 r2. e8( d) |
}

\score {
 \new StaffGroup <<
   \new Staff \with {
     fingeringOrientations = #'(left)
   } { \clef "treble_8" << \voiceOne \upper \\ \voiceTwo \lower >> }
   \new TabStaff \with {
     \override TabNoteHead.font-name = #"Nimbus Sans L Bold"
     stringTunings = #guitar-tuning
     \clef moderntab
   } <<
     \new TabVoice { \voiceOne \upper }
     \new TabVoice { \voiceTwo \lower }
   >>
 >>
 \layout {
   indent = 0
   \context {
     \Staff
     \omit StringNumber
   }
 }
}