The game crashed twice upon entering the nether. Once I entered the nether portal, the nether load screen began to load. When it was just about to complete the load, the game crashed. So I reopened the app, reopened the world, and then  I tried to enter the nether again. Once again, the game crashed. When I tried a third time, it successfully loaded the nether. The world I was using was a world that already existed before the beta started.