Ledger bug

[Rune Zedeler]

After reporting lots of small bug I have found a serious and very
strange one:

\version "1.3.129"
\include "paper16.ly"
\score{
  \notes \context Staff = pr {
         \context Voice < a b c' e'> 
  }
  \paper{ 
    \translator {
        \StaffContext
        StaffSymbol \override #'staff-space = #1.3
    }
  }
}

An extra Ledger line is created between the A and C ledger line, and the
chord looks wrong (a and b overlaps, c moved to the right).
Changing staff-space to 1.33 CORRECTS the bug.
I am really puzzled.

-Rune