Nested Beaming broken (strange behavior!)

[arshiacont]

This snippet fails with strange beam drawings:

{[ \staff<1> (* meas. 1 *)  \clef<"g2"> \key<-3> \meter<"2/4"> 
   \staff<2> \stemsUp \beamBegin:1 \beamBegin:2  a2/32 \staff<1> \stemsDown b&2/32 a2/32 b&2/32 \beamEnd:2 
   \beamBegin:2 \staff<2> \stemsUp a&2/32 \staff<1> \stemsDown b&2/32 a&2/32 b&2/32 \beamEnd:2 \beamEnd:1 
   \staff<2> \stemsUp \beamBegin:1 \beamBegin:2 g2/32 \staff<1> \stemsDown b&2/32 g2/32 b&2/32 \beamEnd:2 \beamBegin:2 
   \staff<2> \stemsUp g&2/32 \staff<1> \stemsDown b&2/32 g&2/32 b&2/32 \beamEnd:2 \beamEnd:1 \bar<measNum=2> 
(* meas. 2 *)  \staff<2> \stemsUp \beamBegin:1 \beamBegin:2 a1/32 \staff<1> \stemsDown b&1/32 a1/32 b&1/32 \beamEnd:2 
   \beamBegin:2 \staff<2> \stemsUp a&1/32 \staff<1> \stemsDown b&1/32 a&1/32 b&1/32 \beamEnd:2 \beamEnd:1 
   \staff<2> \stemsUp \beamBegin:1 \beamBegin:2 g1/32 \staff<1> \stemsDown b&1/32 g1/32 b&1/32 \beamEnd:2 
   \beamBegin:2 \staff<2> \stemsUp g&1/32 \staff<1> \stemsDown b&1/32 g&1/32 b&1/32 \beamEnd:2 \beamEnd:1 ], 
[ \staff<2> 
   (* meas. 1 *)  \clef<"g2"> \key<-3> \meter<"2/4"> _/2  \bar<measNum=2> 
   (* meas. 2 *)  _/2
 ] }

HINT: If I remove one measure there, then it's fine:

{[ \staff<1> \clef<"g2"> \key<-3> \meter<"2/4"> 
   \staff<2> \stemsUp \beamBegin:1 \beamBegin:2  a2/32 \staff<1> \stemsDown b&2/32 a2/32 b&2/32 \beamEnd:2 
   \beamBegin:2 \staff<2> \stemsUp a&2/32 \staff<1> \stemsDown b&2/32 a&2/32 b&2/32 \beamEnd:2 \beamEnd:1 
   \staff<2> \stemsUp \beamBegin:1 \beamBegin:2 g2/32 \staff<1> \stemsDown b&2/32 g2/32 b&2/32 \beamEnd:2 \beamBegin:2 
   \staff<2> \stemsUp g&2/32 \staff<1> \stemsDown b&2/32 g&2/32 b&2/32 \beamEnd:2 \beamEnd:1 ], 
[ \staff<2>  \clef<"g2"> \key<-3> \meter<"2/4"> _/2]
  }