This update is an ongoing shitshow for me. The program to download the update refused to recognize that my macbook had enough space to download it, so I offloaded all my photos (largest data folder) to my external hard drive, and it still wouldn't recognize the open disk space. Reintegrating the photos folder made its own mess. After restarting the computer a few times, the update download finally went through, no idea why or what changed, but when I tried to transfer it to the formatted thumb drive, it threw a "could not read" error at the last second and deleted most of the 34gb file. Trying for the third time to download the update, and it got to 99% and quit again.