Major World Glitch

On one of my saved worlds, a major issue occured where 17 recorded game crashes happened! After building on the nearest Extreme Hills Biome, my Minecraft started to lag. Then, a large square chunk of lag glitched, and I was unable to enter the zone. All blocks in the zone became invisible, so I could see the underground caves and mobs. I am now unable to log back into the saved world, and if I somehow do, it crashes again because Im stuck underground riding a horse.

The seed to this saved world is: omniverse

The crash occurs after building on the closest Extreme Hills Biome mountain to the spawn point.