Waking up my Vivo Note 8 from sleep one evening, I got a nice bright red dialog box saying I had a secure boot signature failure. I clicked OK and got the same screen again, another OK and I got to a recovery screen saying I needed to press the Windows Key to enter UEFI settings. The windows button on the left side didn't work, so I used my handy-dandy OTG adapter to plug in a physical keyboard and got into the BIOS settings. Now I had figured the system was a goner, like perhaps the flash drive had failed. But I was able to disable secure boot, entered my BitLocker key, and booted up. A Windows Update immediately finished applying itself. I am pretty sure but not 100% certain that the night before I had told it to reboot to apply updates. At any rate, it booted into Windows normally, and everything seems fine, all files intact, etc. But I can't re-enable Secure Boot, if I do I get the same error and have to disable it again, but now I don't need to enter the BitLocker key. Does anyone have any idea why this might have happened? I've done a good amount of Googling and I haven't found anything recent that matches my experience (I did find reference to earlier Windows Updates that would fail with Secure Boot enabled, but I haven't heard of anything breaking the signature). Thanks in advance for any help.