Adding reverse spring ... in lilypond 2.6.1

[Juergen Krauss]

I like lilypond very much, but when I create scores with more than 4
parts, I hit a little annoyance.

I use lilypond 2.6.1 on Fedora core 4 and on cygwin.

When compiling the score, I get the following messages over and over
again (see Bassano_42.log):

==================================

programming error: adding reverse spring, setting to unit
continuing, cross fingers

==================================

I was searching this forum and the available documentation, but didn't
get any idea what's going wrong.
In the resulting score, all parts lack any space between clef and 1st
note (from 2nd sustem onwards)

I also attached the source (Bassano_42.ly)

Thank you for sharing your ideas,

Juergen

Bassano_42.ly
Description: application/extension-ly

Bassano42.log
Description: Text Data