When I do:

\setupcolumns[n=2,balance=no,tolerance=verytolerant,rule=on] % and variations
\startext
\startcolumns
abc
\column
def
\stopcolumns
\stoptext

This produces two columns when typeset on the upper half of the page.
Suddenly about halfway the page the columns are not put side by side but below each other!

Is this something known are am I becoming mad?

Hans van der Meer