Sorry if this has been posted before.

I am making a house mod which is using Castle Dour which is working fine and the Thalmor Embassy which is where the problem is, as i go into the first room from the door i linked to Castle Dour (the door you start at in quest) the ceiling has disappeared if i go upstairs half of the hallway has disappeared. It's the same side as the first room so im guessing its the cell but i have no idea what to do about it as im new to modding i have tried before and this same thing happened before i used first Dragonsreach and second was Blue Palace and i just kind of gave up with it.