Line in the middle of the room

[Armin27]

Hello, I have the following problem

I have built a foundation, a new floor (floor 1) and another floor (floor 2), if I want to take a 3D picture of the interior, I have a strange line in the middle of the room which does not disappear want. The foundation has a height of 65cm, floors 1 and 2 each 280cm. Please help!!

[hansmex]

Without having access to your design it's hard to give a good answer.
Maybe a wall from a lower level is sticking through the floor?

H

[Puybaret]

Maybe it's the part of a ceiling which joins the top of walls of different heights.
Did you try to make ceilings invisible?