Problems with SectorPortals

[::Bloodfury::]

Hello.

I have tried to create a two story building via portals.
Everything works quite fine, yet I have some issues.

I have created a collapsed floor on the second floor. You can see down and up from this hole, as well as traverse through it.
But the problem is, when you are at the first floor and move through line portal to the stairwell, the hole in the ceiling
at the first floor renders itself black.

You can see the upper room from the hole if you are in the same sector.
But as soon as you traverse through the line portal and look back, the hole in the ceiling no longer renders the upper floor on top of it.

This is quite funny, because while looking from the hole in second floor, you can see through the line portal downstairs with no problem.

Is this a engine limitation, or should I add more map trickery in order for the portal to be seen even if in another sector.
Sorry for my bad description.

I have included the map as an attachment for you guys to see what I mean. And hopefully someone can provide me a solution on how to fix this.
Thx in advance.