Can't repair file system check exit code 8

Tried to upgrade to Catalina and received the installer error "file system check exit code 8." I attempted to repair the disk with Disk Utility in Recovery Mode, but it didn't work. Also tried to boot into Safe Mode and Verbose Mode, but all that would happen would be a partial loading of the progress bar, then the computer would shut down.

As a last resort, I cloned my drive and installed it onto another iMac via Time Machine — and there is no error, so it's not a system-level software issue. I then wiped the erroring drive and restored from Time machine, and the error persists.

Could the drive be physically failing? Any ideas?

System:

iMac (Retina 5K, 27-inch, Late 2014)

Mojava 10.14.6