Loaded xml with: xmlinclude{problem}{include}{file}

Then called up parts of its contents through a setup:
\startxmlsetups xam:define:get
% The definition is the one with content.
\xmldoiftext{#1}{.}{
  \foundtrue
  \xmlflush{#1}
  \xmlcontext{#1}{.}
}
\stopxmlsetups

The strange thing is that the \xmlflush typesets verbatim the contents of the node called up:

<math version="2.0" xmlns="http://www.w3c.org/mathml"> <apply> <eq/> <ci> f(x) </ci> <apply> <plus/> <ci> 1 </ci> <apply> <power/> <ci> x </ci> <ci> 4 </ci> </apply> <apply> <power/> <ci> x </ci> <ci> 7 </ci> </apply> </apply> </apply> </math>

but, to my surprise the \xmlcontext{#1}{.} lets it disappear completely. So does \xmlflushcontext{#1}. In other parts of the program \xmlcontext does what it should do, thus the mkvi format seems ok.

What could have happened? Some detrimental effect of the \xmlinclude?
Hans van der Meer