I'm also getting with my kernel. I don't think it's kernel related, since flashing other things (ARISE Magnum Opus with magisk compatiblity enabled, specifically) can trigger the same reboot regardless of the kernel I'm using. I haven't had time to pull my own logs yet, but I do know that it's rebooting to recovery for a factory data reset (at least in my case). Currently, I think it's one of Oreos new security features being triggered, and going down to wipe to protect the device. The only hole in my theory is that it doesn't happen with stock Oreo.
EDIT: After scrolling through Franco's thread, I found that his kernel seems to be triggering the same (or similar) behaviour on stock. This hardens my theory that it's a new O security measure, since you and I are using a common kernel base source (your 8.0 base branch

), but Franco isn't, making it less likely to be something in the source.