Windows/walls missing from apartments - sims 4 eco lifestyle

Hello, 

I recently moved a new family into one of the apartments in the eco lifestyle pack. 

I chose to bulldoze the apartment so I could give it a fresh start (as I do with other apartments in city living etc).

When I went into build mode the whole apparent had disappeared, although I fixed this by building a singular tile wall, but now the apartment is missing windows from the back walls, which are there in the apartment next door, and on the floors of the block below. It also won't let me place windows here because I 'cannot edit the outside of the lot'. 

Has anyone else had this glitch/issue, and if so, how did you fix it?

Cheers