fprintd-enroll gives Enroll result: enroll-unknown-error (incl. prototype output) about validity90 HOT 1 OPEN

I'm having the exact same issue: Arch Linux, Thinkpad 25 (Anniversary Edition), Validity Sensors 138a:0097. I'm attaching the output of prototype. I scanned only my right index finger, multiple times, with one LED test at the end.

2018-09-14_prototype_run.txt

I did manage to get my finger enrolled, but I had to fully enroll it in Windows Hello (VirtualBox Windows 10 guest). I was able to enroll my right index finger in Arch, but it only accepted one swipe, not five like I expected. At first, fprintd-verify accepted/matched my fingerprint consistently. Now, after some kernel upgrades and requisite reboots, fprintd-verify only reports "no match." Windows Hello also will not work. Not sure if the fingerprint scanner has an internal memory or not, but it appears to have something like that.

from validity90.