Most common reasons
- Dirty sensor or oily/wet finger
- Finger enrolled poorly (single angle)
- Low battery reducing sensor stability
- Finger condition changes (dry skin, cuts)
Fix steps
- Clean sensor with microfiber cloth.
- Delete the fingerprint and re-add it.
- Enroll the same finger 2–3 times at different angles.
- Add a second “backup” finger.
- Replace batteries if behaviour is inconsistent.