I often face this issue. The fingeprint sensor does not work and sometimes the touch also misbehaves when phone is charging.
Why does this happen and how to fix this?
I experienced this issue with Mi Note 4, as well as Redmi 4A.
asked Nov 26, 2018 at 8:30
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1Regarding "touch also misbehaves when charging", I believe it also applies on many devices (including my Nexus 5) on certain condition. I still cannot pinpoint the issue because there are so many factors: charger, USB cable, voltage, amperage, wattage, etc.– Andrew T. ♦Commented Nov 26, 2018 at 12:34
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3 Answers
As requested by OP posting answer, in response to my comment (now deleted) based on my experience
Having a clean power supply, using original charger + USB cable, setting up finger prints again are the common things that work...
I am not sure as to why touch sensor works only with original charger but posting as it may help, as it helped OP
answered Jan 3, 2020 at 7:16
Don't know the exact answer but from my experience It seems that touch sensors are finely tuned and calibrated against voltage reference. Using power supply other than provided chargers might be affecting these calibrations and cause fluctuations that results in malfunctioning of touch screen - that is - we click on something and something else is clicked or sometimes touch doesn't work, etc.
answered Jan 3, 2020 at 7:30
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+1. You have a point. It's called Ghost touch. See android.stackexchange.com/a/156880/131553 Commented Jan 3, 2020 at 9:52
Something I have noticed with my fingerprint sensor is that if phone is face down and hasn't been used for a short while, phone will not read finger print until phone is actually picked up. Not sure if because of proximity or orientation sensor, but appears to be that way to keep from accidental unlocks. Is your phone face down when attempting to unlock? Also, what do you mean by "touch misbehaves"? If you mean the entire touchscreen and then combined with fingerprint sensor this could be pointing to your device being defective.
