This is a very short fix but a common issue.  DS engine uses a miminum of model parameters to render, so
you may find flipped faces or incorrect orrientation during run time.  These are caused by rotating, flipping,
mirroring in gmax.  These orientation changes are not properly interpreted by DS engine.  To fix these, you
must restore a virgin unmodified pivot point to an object.  Here is the procedure I use:

1.  create a plane, size and position does not matter
2.  align the plane's pivot point to the x y z of the pivot point of the object to fix
3.  set the color of the plane to that of the object
4.  copy the object's name to the plane
5.  copy the object's uvw modifierm if present, to the plane
6.  select the plane, covert it to an editable mesh
7.  click attach in the editable mesh rollout
8.  click the object to attach it
9.  delete all the polys of the new plane


Your orientation is now set correctly to work with DS engine.  This usually fixes flipped normals too.
If you need a more detailed step by step, ask me.

Note that you will have to re door/floor nodes.  It is best to delete any sno modifiers
and create anew.