This is a very old bug. :)
To prevent bots from going "through" obstacles, we use so called
collision-rectangles which the bots cannot walk through.
(Almost) Every obstacle has such a collision rectangle assigned to it, the
problem with the door is that it has two door-posts which would need two
collision-rectangles for this obstacle which is not yet supported in any way.
So we only have one collision rectabgle for the door which means that the droids
will be able to walk "through" one of the posts.