(MacBook Pro 13" late 2013, 8 GB RAM, i5 2.4 GHz) Hi all! I recently got a 1 TB Seagate Backup Plus external SSD and was planning to install Mojave on it. After plugging it in for the first time, I opened Disk Utility to change the partition map from MBR to GUID and then started up the installer. The drive's icon was greyed out and the installer told me that I couldn't boot up from it, so I opened Disk Utility again to see what's wrong. I noticed that the EFI partition was now missing for some reason, which I guessed was the cause of the problem. I wasn't sure what to do at this point, so I tried to erase the drive again, but the process failed with a "couldn't unmount disk" message. Then I tried to erase it via Terminal, but again, the operation timed out while unmounting the drive. What's worse, when I unplugged it and then plugged it back in, the drive didn't show up on Finder or Disk Utility, though it's still listed when I entered the diskutil command on Terminal (only the size, no volumes listed). Any idea what's happening here? Thanks a lot in advance!