Hi, So this issue has been going on for a long time and I'm slightly going crazy. When I first got my iMac (a 27" 5K, Late 2015, currently running macOS 10.12) I immediately split my fusion drive so I would get 1 dedicated SSD and 1 HDD. This might be where the issues started. However, a few months ago I also wanted to install Windows 10 on my Mac with Bootcamp. I remembered everything went great on my MacBook, so I figured it should work just as good on my Mac. Then I tried to create the bootable USB with bootcamp and I've seen every error you can imagine. After a day of stress, I just gave up then. Yesterday though, I wanted to give it another shot. So I tried creating the USB with the Bootcamp Assistant and I got the same errors I got months ago. So I thought, why can't I create the USB on my MacBook. So that's what I did. I made the Bootcamp USB with Windows 10 via the Bootcamp Assistant on my MacBook. When I try to install Windows on my iMac now with the USB I just created, I'm getting another error: "Your disk could not be partitioned. An error occured while partitioning the disk. Please run Disk Utility to check and fix the error". I already tried using 'First Aid' in Disk Utility, but that didn't help. I also tried booting up in Single User and running the /sbin/fsck -fy command, but that didn't help as well. I also tried creating a different USB on my MacBook (now a 2.0 flash drive, the previous one was a 3.0 flash drive), but still getting the same error. The drive I want to install Bootcamp on is a completely empty HDD, so that should make things easy, right? I really hope one of you Mac wizard will be able to guide me to a solution. Many thanks in advance!