This has been happening for a very long time now (maybe a year or two, maybe longer?).
When KLCK is enabled and I unlock my phone (KLCK opens+is dismissed, system lock screen authenticated using PIN or fingerprint, OR using fingerprint while screen off, bypassing the lock screens), the fingerprint prompt will appear in several different ways in order of rarity:
- Quickly flashes on screen and disappears
- Flashes on screen and waits to be dismissed manually, either scanning fingerprint or tapping outside the prompt
- Flashes on and off for a long time, from a second or two to until System UI crashes
This does not happen when KLCK is disabled with the in-app toggle.
- LG v60 ATT (root)
- Android 11
- KLCK 3.74b323017