Cross-staff notation with tremolos ruins beam positions

[Daniel Woodfield]

I was trying to write something in which eighth notes with a single 
tremolo on them (16ths) alternate between staves using \autochange or 
manual staff change.  Both absolutely wreck the positioning of stems and 
beams.  For a simple example of the problem, type in Lilypond 2.20.0:

\autochange { c8:16 c'':16 c:16 c'':16 c:16 c'':16 c:16 c'':16 }

Thank you for your help!