stemNeutral problem

[Edward Neeman]

Hello,

I’ve come across some weird behaviour from the \stemNeutral command. This 
doesn’t work:

%%%%

\version "2.19.82"

\relative {  \stemUp <g' bes d>8) r8
     \acciaccatura { \stemDown <ges' bes>8 } \stemUp <c e g!> r
    \stemNeutral c,16 es ges bes }

%%%

Adding a second \stemNeutral command is necessary to reset the stems to normal. 
Why might this be?

Thanks,
Edward

---
Dr. Edward Neeman
www.neemanpianoduo.com