Hello, I have a problem with a xiaomi redmi 5 plus 4/64 phone, the phone does not charge until the end usually stops at 97% but this number can change although it does not fall below 90%. The second problem is that the phone can turn off for no reason (usually with a lower battery percentage) and cannot be turned on until it is connected to charging.
I was able to charge the phone to 100% by method after charging to the max, disconnect the phone from charging and turn it on plug it in again for charging charge to the max disconnect turn off and recharge to the max and up to 100% As for turning it off, I discovered that it does it with 30% battery and after turning it on 0%, besides, the phone withstands less as much battery as it should, so the full battery cycle closed between 30 and 100%
As for self-deactivation, remove the clapper at the back and press the battery connector. Recently, I had several pieces of this model where such circuses happened to clients. It was enough to plug in and unfasten.