Tes construction kit problem

Iv been searching around the web for an answer to no avail so I said id try and find an answer through morroblivions site. I have everything properly installed and am having great fun playing but yesterday I decided to make myself a morrowind residence on my own floating rock. The problem was that I couldn’t and still cant use any of the frostcrag spire buildings for it. I can place all of them down and those items from the shivering isles which is the other items I use but when I save it comes up with a long ‘assertion message’ asset at e……. the rest is nonsense. And when I either retry to save until the message goes away or ignore it the items are not in the game when I load it up.When I then go back to the CK the items I added namely the tower aren’t there.

If anyone knows what I was doing wrong it would be greatly appreciated