First of all, according to your description should be the data cable or mobile phone tail plug (that is, the data cable jack) problem, first use someone else's data cable to try, if it is the data cable problem, change the line, if it is still poor contact, then it should be the tail plug is broken. In addition to your situation, there may be 1. Hardware failure, power management chip problems lead to inaccurate power monitoring.
2. System problems, some third-party ROM drive is not perfect, read electricity is not accurate.
3. Mobile phone power consumption is huge, if you use a small power charger to charge, while the mobile phone is carrying out a large number of operations, such as playing big games, brushing the machine, opening wifi hotspot and so on.