the first cartouche collides with the heading. Does this patch (not yet committed) solve the problem in your real file? (It fixes the test file, thanks much for the reduction.)
k --- texinfo.tex.~1.347.~ 2011-07-08 08:58:52.000000000 -0700 +++ texinfo.tex 2011-08-14 17:23:58.000000000 -0700 @@ -6275,2 +6274,8 @@ end \let\nonarrowing = t% + % + % If this cartouche directly follows a sectioning command, we need the + % \parskip glue (backspaced over by default) or the cartouche can + % collide with the section heading. + \ifnum\lastpenalty>10000 \vskip\parskip \fi + % \vbox\bgroup
