DSM session with scroller issue

This is not a C question per se, but I'm hoping to find some fellow DSM
enthusiasts here.

I'm drawing some windows with DSM and I have an issue with one of the
windows containing a scroller.
This window is created with the Create session API during program startup
without being immediately displayed. It is displayed (or started, in DSM
terms) later when the user presses an Fkey.

The problem is that when it's started the first time it's displayed as
empty, even though data has been written to the scroller. If I move the
window (the Move Window by User API) the scroller is displayed, as it also
is if I the user ends the window and then starts it again.
There are no exit routines associated with the session, that is I'm only
writing to the scroller once during the program startup so I'm not redrawing
the window when it's moved or restarted. That's taken care of by DSM. I've
tried using the draw_fp exit routine for my "loadScroller" function but that
still doesn't display it the first time it's started, only on subsequent
"moves" or restarts.

Anyone that's got a clue? And any general pointers on the sequence of API
calls for handling a session with a scroller in general would also be most
helpful.

Regards,
Erik