Hey TheDiadem,
This was investigated and was determined to be caused by corrupted files, which was explained here. I am sorry that you have to redownload the files, but you can try the steps listed there to reduce the amount required to download again. Unfortunately if those steps don’t help, there is no other work around other than to redownload the entire game. I understand that this is frustrating for customers with limited bandwidth but that is outside of our control.