That's great news, thanks for taking the effort in sharing the screenrecording!
I do have 1 request - can you please flash the latest
PHH GSI & report if you're able to boot; if this is the case, whether the fingerprint works as well?
Once you download the image, you can flash it via fastboot (after uncompressing it with 7zip):
fastboot flash system downloaded_file.img
You will also probably need to factory reset to avoid bootloops:
fastboot -w
v4.12 is the same build you based your instructions on - maybe this was fixed with the monthly security update?
Have you applied any OTA since? If you did, & since you encountered issues with the fingerprint sensor, would you be in a measure of trying relocking/unlocking again, & confirming whether the fingerprint sensor works for you after rooting?