I went to create a new world and added the "Chroma Hills" resource pack with the 64x setting. The game crashed whilst creating the world. After further testing the problem was definitely the pack and not the world as it also crashed when loading the pack into global resources. I tried deleting the pack and downloading it again but still no luck it keeps crashing. This is a marketplace pack so it should be working for the people who have bought it. 

Edit: this is also a problem with the 128x version