wrong order of content-list items if using balanced columnsets

[Vit Zyka <vit.zyka@seznam.cz>]

Hello Wizards,

the next example illustrates the problem with wrong order of 
content-list items if using balanced columnsets:

-----------------------------------------------------------------
\setuplayout[grid=yes,topspace=1cm,bottomspace=1cm,height=middle]
\showgrid

\definecolumnset[A][n=2,balance=yes]
\setupcolumnsetlines[A][1][1][21]
\setupcolumnsetlines[A][1][2][21]
\definecolumnset[B][n=2,balance=yes]

\starttext
\startcolumnset[A]
   \section{Knuth}
   \dorecurse{2}{\input knuth \endgraf}
\stopcolumnset
\placeongrid{\hairline}
\startcolumnset[B]
   \section{Zapf}
   \dorecurse{1}{\input zapf \endgraf}
   \blank
   Content:
   \placecontent[criterium=all]
\stopcolumnset

\stoptext
--------------------------------------------------------------------

Problem is that the second section (Zapf) is inserted to .tui before the 
first one (Knuth). My observation: on the page where one columnset (A) 
is closed by \setupcolumnsetlines and the second (B) continues, .tuo 
contains marks from B firstly. This makes book content unsable in this 
configuration.

Any solutions? I am thinking about: Proper order writting to .tuo or to 
sort items according to mark number - it is correct (not sure if it is 
implemented?).

Thanks
Vit