Game shuts down when deleting walls

As it says in the title, the game just turns off when I delete walls on a specific lot. I've tried repairing it, repairing the app etc. I have no mods or custom content. 

The only difference with this lot is that I downloaded it from the gallery. I definitely don't have the time or capability to build this so I'd rather not delete it if I can avoid it! Can someone tell me why this is happening? How can I fix this so I can delete a couple of walls and move some parts around?

Thank you!