Mojave Update Failure (Kernel Panic/Boot Loop)

I ran into a really big issue with the update last night (that has continued into today):

When installing Mojave from the latest version of High Sierra (10.13.6), I received this error while installing: com.apple.DiskManagement error -69874. It told me everything was fine and I'd go back to High Sierra after reboot.

I followed the prompts, it rebooted. But instead of returning to High Sierra, it would show the apple logo, and then the kernel panic screen. It would reboot again, show the apple logo, and then kernel panic again. This went on for a couple of minutes before it eventually showed me the no-disk "do not enter" circle.

I was able to boot into recovery mode after a hard reset. Ran the First Aid in Disk Management. Rebooted. Same deal. Apple Logo > Kernel Panic > No disk.

I then tried a reinstall of High Sierra from a USB drive without a reformat. No change, same issue.

I know fusion drives weren't APFS supported beforehand, so I figured that it's probably something to do with an issue formatting from HFS+. If I have to reformat, I may as well update at the same time. So, I made a new USB installer for Mojave, and have reformatted the fusion drive as APFS, and am now pulling nearly a TB of data from my time machine backup. Hopefully, when that's done, my mini will boot again.

My system is as follows:

2012 Mac Mini (i5)

"nonstandard" Fusion drive (128 SSD + 1TB HDD)

16GB RAM