problems with a Bosch WTL5200SN/04 Tumble Dryer?

When we use our Bosch WTL5200SN/04 condense Tumble Dryer
(FD 7711 00715) the water ends us in the area behind the
condenser instead of in the water container at the top
(which pulls out for emptying) and the red light indicating that
the container is full goes on even when the container is totally empty. Among the possible causes for this, I can imagine the
following:
> Some pump which transfers the water up to the container
is not working properly.
> There is some kink in the tube which goes up to the
container (although I cannot see any such kink).
What other problems might be involved here? And how can
I diagnose this situation?
Thankful for an answer as soon as possible,
Joe