Chord tremolos

[Chris Jackson]

In the following example, why do the unfolded repeats fit into the first two
bars, but I get "barcheck failed" errors for the third and fourth bars with
tremolo repeats?  (18+6)*2 / 32 = 12/8 ?

\version "1.7.30"

\score
{
 \context Voice \notes \relative c {
     \time 12/8
     \repeat "unfold" 18 { c'32 f32 } \repeat "unfold" 6 { b32 e32 } |
     \repeat "unfold" 18 { c,32 f32 } \repeat "unfold" 6 { b32 e32 } |
     \repeat "tremolo" 18 { c,32 f32 } \repeat "tremolo" 6 { b32 e32 } |
     \repeat "tremolo" 18 { c,32 f32 } \repeat "tremolo" 6 { b32 e32 } |
 }
}

-- 
chris