High Sierra Beta 9... one computer will not finish install and is constantly rebooting

Same here on my 2015 MBP. Did you or someone else find a solution?

I had the same problem. I tried restoring from Time Machine (would have been backed up on beta 8), let it run overnight, and this morning, bootup ends with a prohibitory screen.

So I tried reinstalling using disk utility, but that failed with an error.

I'm not sure what to do next. Does my time machine backup need to be restored only over 10.13?

What are your planned steps to properly recover?

Had the same issue with my MacBook pro, best bet is to start the system in Safe Boot and run the update through the App Store, fixed it for me. Seems to only be coming from this last update. Hope this helps.

Does it appear to be trying to flash the system firmware? The screen looks like a low resolution Apple grey update screen with a progress slider. Is your system long beeping before reboots?

I had the exact same issue. When I used the suggestion to start in safe mode and reinstall, I was able to complete my install as intended. I was also installing on a MacBook Pro that has an encrypted hard drive.