Jens - I believe that there is currently no way to fix this fill on standard parts - I had hoped that this condition would be fixed with an update - but no luck so far. The usual way is to edit the GDL code of the door leaf, removing the fill. I searched and could not find where the offending fill was written.
I know this doesn't help - perhaps someone smarter than I could figure it out.
Lew Bishop
AC9/ P4-2.53 nVidea 440 XPPro