World not loading. Stuck on loading screen

I have been working on this guardian farm for a while now. Today, when I logged out of my world and then back in, I kept getting stuck on the loading screen. The only way that I could close Minecraft was to force quit. Luckily, I have a back-up for my world, but anytime I import and make any changes in the world, I run in to the same problem. I can't play the game until this is resolved, and I am not sure what to do.