My Fingerprint scanner on Note 10 plus works perfectly fine in all conditions.. wet/dry/sunny/hot.. sometimes i have issue unlocking my phone because either i am not holding it long enough or not in the right area.. but that's very rare.. and when it does not detect in 1st attempt we need to keep the finger for a very long time when unlocking in the 2nd attempt.. may be to make sure its the correct fingerprint..
Ultrasonic fingerprint sensor is used by
Samsung in its Flagships because it has superior technology compared to Optical fingerprint scanner used by other chinese brands.. It is more secure and works even when your hands are wet.. Optical fingerprint scanner does not work when your hands are wet or its raining and you are trying to unlock your phone.. Optical scanner might be faster than ultrasonic but that does not mean it is better..
Tips - It unlocks faster if we use the same fingerprint everytime.. and people facing issues might try to register same fingerprint twice in settings as you can see from the screenshot attached i have registered Right Thumb twice as i use it most of the times for unlocking my device.. it helps!
P.S. - This is just my experience.. Tell yours in the comments below..
Thank you.
