World won't load, stuck on "Building Terrain" screen

Noticed the world was starting to be a bit slow at loading over the weekend, resulting me in resetting the Xbox & Minecraft, before trying to reload into the world which seemed to fix it. However today, the world will now not loaf at all. I've made a copy of it to see if that helps, I've reset my Xbox & Minecraft with no luck, it just constantly gets stuck on the "Building terrain screen".