Open the launcher program, run the game, hit singleplayer then select world, get to Loading World Building Terrains then game crashes and brings back to launcher. Ran log and got: Keeping entity minecraft:pig that already exists with UUID d526d885-4e9f-4d19-8866-d4ef197bdfc2 in the debug message. Attempted to fix issue in MCedit but unable to run the plugin that fixes said issue.