Feathered beams with tuplet fractions

[Qian Li]

Why does lilypond choke on feathered 8:10 notes but handles 4:6 no problem? The first example works (even the slur works), but the second doesn't. 

Thanks.
Qian

\times 4/6{  
\featherDurations #(ly:make-moment 6 8 ) {    
\once \override Beam #'grow-direction = #RIGHT 
 bf16 ( ef g bf' g ef   
} 
} 
cs,2) 

%second example

\times 8/10{
\featherDurations #(ly:make-moment 6 8 ) {
\once \override Beam #'grow-direction = #RIGHT
as'16 ( bf cs bs as bs as g fs g }
}
fs4)