\repeat percent {} breaking \drummode context

[Uwe Falke]

Trying to save some space and simplifying the scores,
but either I am doing something wrong / odd, or there is a bug.
Everything following the \repeat percent {} in the example below is  
set to separate staffs with clefs, i.e. nit in drummode anymore.
Yep, I know my version is quite outdated but as I have not found any  
mentioning of such a behaviour in the web I might doing it wrong and  
it has nothing to do with the version.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.12.3"

#(define mydrums '(
(bassdrum default #f -3)
(snare default #f 1)
(hihat cross #f +4)
(closedhihat cross #f +4)
(openhihat cross "open" +4)
(crashcymbal xcircle #f +6)
(ridecymbal harmonic-black #f +5)
(ridecymbala harmonic #f +5)
(hightom default #f +3)
(highmidtom default #f +2)
(lowtom default #f -1)))
drh = \drummode { cymr8.^"crash" hhc16^"h.h." hh hhc8 hho hhc8 hh16 hh  
hhc4 r4 r2 }
drl = \drummode { bd4 sn8 bd bd4 << bd ss >>  bd8 tommh tommh bd toml  
toml bd tomfh16 tomfh }

\new DrumStaff = main <<
  \set DrumStaff.drumStyleTable = #(alist->hash-table mydrums)
  \new DrumVoice = "1" { s1*2 }
  \new DrumVoice = "2" { s1*2 }
  \drummode {
\partial 4 sn4 |
  \repeat volta 2 {
      << { \repeat unfold 8 hh8 } \\ { bd4 sn4 bd4 sn4 } >>
      << { hh8 hh hh hh r hho r hho } \\ { bd4 sn4 bd4 sn4 } >>
    }
 % That seems to break drummode ...
   \repeat percent 6 { << { r8 cymr8 r cymr r cymr r cymr } \\ { bd4  
sn4 bd4 sn4 } >> }
  << { cymr8 r8 \repeat unfold 6 hh8 } \\ { bd4 sn4 bd4 sn4 } >>
   }
> >
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Thanks for any help.

Uwe

--