Yep, I just noticed this too. It's quite easy to replicate.
A simple room with a couple of sectors thrown in that have the same properties as the main room.
Two smaller sectors are not required - it's just what I did because I wanted to see if line-facing made a difference (which it didn't).
UDB:
In game, it looks like this:
If I open the map screen without moving, it looks like this:

The area inside the smaller sectors is not being shown and it's like the top-most square has hidden the main area floor behind it.
After moving around the map, it looks like this:
Most of the floor is now visible, except the areas inside the smaller sectors (as you can see, I'm standing inside one of them and the floor is still not being shown).
Yep, I just noticed this too. It's quite easy to replicate.
A simple room with a couple of sectors thrown in that have the same properties as the main room.
Two smaller sectors are not required - it's just what I did because I wanted to see if line-facing made a difference (which it didn't).
UDB:
[imgur]https://imgur.com/5ujnPNG[/imgur]
In game, it looks like this:
[imgur]https://imgur.com/2B9Nk6h[/imgur]
If I open the map screen without moving, it looks like this:
[imgur]https://imgur.com/vAG0moN[/imgur]
The area inside the smaller sectors is not being shown and it's like the top-most square has hidden the main area floor behind it.
After moving around the map, it looks like this:
[imgur]https://imgur.com/lALdXFL[/imgur]
Most of the floor is now visible, except the areas inside the smaller sectors (as you can see, I'm standing inside one of them and the floor is still not being shown).