My goal was to revert my HTC One to stock, no tampered, no locked, etc. After hours of trying to find a solution to S-Off, I was finally successful with gaining S-Off, Removing the Tampered Flag, Re-locking, and returning to S-On.
I'm not entirely sure what happened next. I think I most have chosen "reboot" so that I could get back in and apply a new RUU.
Instead, my phone returned to bootloader, with a surprise reappearance of the "Tampered" flag, and a new one now, "Security Warning".
Attempts to reboot simply return me to bootloader. Attempts to access Recovery return me to bootloader. Attempts to power down work. And when I power on again it returns me to bootloader.
What. The. Hell. Happened.
Thanks in advance for any help.