Emmanuel,

I think I found a small bug in v3.4 b11 that concerns creating a room.
In the attached file the outline of a building is drawn. You will find that it is impossible to create a room by double-clicking inside this shape.

If you inspect the connection of the two wall segments marked with a red circle, you will see that this connection isn't at a 90 degree angle, but is slanted or skewed. It looks a bit like a problem you fixed earlier.

Now, if you bisect the room, you will find that you can create a room by double-clicking in the part without the red circle, but NOT in the part where the slanted connection is.

Hans