Missing noteheads

[tiM]

Hi, i think i found a very strange bug using lilypond-book. Now i'm just new
at lilypond, but the inconsistency makes me think it's not my fault, still
i'm aware that it could well be me doing something wrong.

The following code leads to an output with missing noteheads and time
signature and fingering in courier new.

\begin{lilypond}
\relative c'{
 \context RhythmicStaff {
  \override Staff.TimeSignature  #'style = #'()
  \time 4/4
g4_4 g_4 a_5 a_5 g2_4 e_2 
}
}
\end{lilypond}

While the exact same code placed twice leads to the output I expected from
the input above.

\begin{lilypond}
\relative c'{
 \context RhythmicStaff {
  \override Staff.TimeSignature  #'style = #'()
  \time 4/4
g4_4 g_4 a_5 a_5 g2_4 e_2 
}
}
\relative c'{
 \context RhythmicStaff {
  \override Staff.TimeSignature  #'style = #'()
  \time 4/4
g4_4 g_4 a_5 a_5 g2_4 e_2
}
}
\end{lilypond}

How is this possible?

Tnx. tiM