String number indication stuffs up cross-staff kneed beam

[Nick Payne]

See below. The output is fine until I add the '\3' string number 
indication to the last note on the lower stave, at which point the 
output gets garbaged. The problem doesn't happen if the string number 
orientation is set to down rather than up, nor does it happen with a 
kneed beam on a single staff with the string number orientation up.

\version "2.13.51"

notesHigh = \relative c'' {
    \stemUp bes32[ r g' fis]
}

notesLow = \relative c'' {
    \override Fingering #'staff-padding = #'()
    \override StringNumber #'staff-padding = #'()
    \override Fingering #'add-stem-support = ##f
    \override StringNumber #'add-stem-support = ##t
    \set fingeringOrientations = #'(up)
    \set stringNumberOrientations = #'(up)
    \stemUp
    \change Staff = "high"
    \stemDown bes32[
    \change Staff = "low"
    \stemUp <a-1> <c-4\3>16]
}

\score {
    \new PianoStaff <<
        \new Staff = high {
            \notesHigh
        }
        \new Staff = low {
            \notesLow
        }
>>
}


Nick

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bad.png
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